Using ClustalX for multiple sequence alignment

Jarno Tuimala
December 2004

All rights reserved. The PDF version of this leaflet or parts of it can be used in Finnish
universities as course material, provided that this copyright notice is included. However,this publication may not be sold or included as part of other publications without
permission of the publisher.

2

IndexIndex................................................................................................................................... 3
Quick Start ........................................................................................................................ 4
1. Open ClustalX............................................................................................................. 4
2. Read in the FastA-formatted sequences...................................................................... 4
3. Modify the output format option, if necessary............................................................ 5
4. Create an alignment .................................................................................................... 5
Creating the input file for multiple sequence alignment ............................................... 6
Multiple alignment theory................................................................................................ 7
Getting the data into ClustalX......................................................................................... 8
Setting up the alignment parameters .............................................................................. 9
Pairwise alignment parameters ....................................................................................... 9
Multiple alignment parameters ..................................................................................... 11
Alignment output-format .............................................................................................. 12Creating the alignment ................................................................................................... 13
Writing alignment as Postscript .................................................................................... 14
Assessing the quality of the alignment .......................................................................... 15
Advanced alignment strategies ...................................................................................... 16
Advanced options ............................................................................................................ 17
Do alignment from the guide tree ................................................................................. 17
Profile alignment........................................................................................................... 17
Using secondary structure information in the profile alignment .................................. 19

3

Quick Start
In order to make a multiple sequence alignment using ClustalX, you should have yoursequences in FastA format. If you do not know haw to do this, check the chapter“Creating the input file for multiple sequence alignment”.
1. Open ClustalX
After starting ClustalX, and you will see a window that looks something like the one
below.

2. Read in the FastA-formatted sequences
Pull down the File-menu, and choose Load Sequences menu item. Navigate to the folder(subdirectory) that contains the input file (text-file containing the sequences in FastAformat), and choose that file. Sequences should appear in the ClustalX window.

The left pane (in the figure above) lists the sequences according to the name that follows“>” symbol in the input file. The right pane shows the beginning of each sequence. You
can scroll to the right to see the rest of each sequence by using the scroll bar at the bottomof the pane.

43. Modify the output format option, if necessary
Before aligning the sequences, you should make sure the output format options (frommenu Alignment -> output format options) are set correctly. If you’d like to continue
with phylogenetic analysis using Phylip package, you should select PHYLIP format.
Note, that you should always save the Clustal formatted sequence alignment, also. Here’s
an example of the output format option settings:

4. Create an alignment
In order to make the actual alignment, select “Do complete alignment” from the menu
Alignment. At that point ClustalX asks for output file names. Your sequence alignment is
automatically saved in those files once the alignment is ready. After the alignment has
been successfully calculated, a new view will appear, and it might look something likethat:

Now that the alignment has been created, you can close ClustalX, and use the generatedalignment files in other programs.

5

Creating the input file for multiple sequence alignment
Here, ClustalX is going to be used for sequence alignment. It, like any other computer
program requires the data it manipulates (the input file) to be in a format it can recognize.
You can use your favourite word processor to create the input file, but I use Notepad.
In the previous chapters, we pasted the found sequences into the text editor. Often theunedited files look like this:gi|15146064|gb|AY040893.1| Homo sapiens individual VP37 mitochondrial control region
GGTCTATCACCCTATTAACCACTCACGGGAGCTCTCCATGCATTTGGTATTTTCGTCTGGGGGGTGTGCACGCGATAGCATTGCGAGACGCTGGAGCCGGAGCACCCTATGTCGCAGTATCTGTCTTTGATTCCTGCCTC
ATCCTGTTATTTATCGCACCTACGTTCAATATTACAGGCGAACATACCTACTAAAGTGTGTTAATTAATTAATGCTTGTAGGACATAATAATAACAATTG gi|15146065|gb|AY040894.1| Homo sapiens individual
mitochondrial control region
GGTCTATCACCCTATTAACCACTCACGGGAGCTCTCCATGCATTTGGTATTTTCGTCTGGGGGGTATGCACGCGATAGCATTGCGAGACGCTGGAGCCGGAGCACCCTATGTCGCAGTATCTGTCTTTGATTCCTGCCTC
ATCCTATTATTTATCGCACCTACGTTCAATATTACAGGCGAACATACTTACTAAAGTGTGTTAATTAATT

VP5ClustalX can recognize several formats for the sequences, but we will use the FastA
format, because that’s the one most easily downloaded from the databanks. The FastA
format can be recognized, because the first line begins with the “>” character. This line
contains the title of the sequence. The sequence will start from the next line. The “>”character should be followed by one word (only letters or numbers and _), which
ClustalX will use as the name for the sequence in the multiple alignment that it creates.
Clustal treats everything between “>” and the first space as the sequence name. I suggest
you to save the original title, and just enter the new name (up to 10 characters but notmore) for the sequence and one space after that. This way you can still save the Genbank
accession number in the same file as the sequences. You will need the accession number,
if you’re ever going to publish your results, so save them!
For the sake of clarity, we will put a blank line after the first sequence before the second
sequence. The order of the sequences in the file is not important.
After these formatting procedures, the aforementioned sequences should look like this.
>hs_vp37 gi|15146064|gb|AY040893.1| Homo sapiens individual VP37 mitochondrial control
GGTCTATCACCCTATTAACCACTCACGGGAGCTCTCCATGCATTTGGTATTTTCGTCTGGGGGGTGTGCACGCGATAGCATTGCGAGACGCTGGAGCCGGAGCACCCTATGTCGCAGTATCTGTCTTTGATTCCTGCCTC
ATCCTGTTATTTATCGCACCTACGTTCAATATTACAGGCGAACATACCTACTAAAGTGTGTTAATTAATTAATGCTTGTAGGACATAATAATAACAATTG>hs_vp5 gi|15146065|gb|AY040894.1| Homo sapiens individual VP5 mitochondrial control
GGTCTATCACCCTATTAACCACTCACGGGAGCTCTCCATGCATTTGGTATTTTCGTCTGGGGGGTATGCACGCGATAGCATTGCGAGACGCTGGAGCCGGAGCACCCTATGTCGCAGTATCTGTCTTTGATTCCTGCCTC
ATCCTATTATTTATCGCACCTACGTTCAATATTACAGGCGAACATACTTACTAAAGTGTGTTAATTAATT

Save the sequences in this FastA-format as a plain text file (also known as ASCII). In thecurrent Word version XP, the sequences should be saved as plain text, and then theencoding should be changed to MS-DOS in order to make sure that the file works inevery system.

6

Multiple alignment theory
Dynamic programming can be used to align multiple sequences also. It creates an optimalalignment, but cannot be used for more than five or so sequences because of thecalculation time. Therefore, progressive method of multiple sequence alignment is often
applied.
Clustal performs a global-multiple sequence alignment by the progressive method. The
steps include:a) Perform pair-wise alignment of all the sequences by dynamic programmingb) Use the alignment scores to produce a phylogenetic tree by neighbor-joiningc) Align the multiple sequences sequentially, guided by the phylogenetic tree
Thus, the most closely related sequences are aligned first, and then additional sequencesand groups of sequences are added, guided by the initial alignments to produce a multiple
sequence alignment showing in each column the sequence variations among thesequences.
Sequence contributions to the multiple sequence alignment are weighted according totheir relationships on the predicted evolutionary tree. Weights are based on the distanceof each sequence from the root. The alignment scores between two positions of themultiple sequence alignment are then calculated using the resulting weights as
multiplication factors.
As more sequences are added to the profile, gaps accumulate and influence the alignmentof further sequences. Clustal calculates gaps in a novel way designed to place thembetween conserved domains. Gaps found in the initial alignments remain fixed. New gaps
are then introduced into the multiple alignment when more sequences are added, but gaps
can never be deleted, only added. Clustal also implements methods, which try tocompensate for the scoring matrix (e.g., PAM), expected number of gaps, anddifferencies in sequence length.
Clustal has advanced options:a) Add sequences with weightb) Add weights to different sequence positionsc) Add a sequence or alignment to an alignmentd) Use user-defined tree for alignment
Some of these will be discussed in the next chapters.
The problem with progressive alignment is the dependence of the ultimate multiple
sequence alignment on the initial pair-wise alignments. The very first sequences to bealigned are the most closely related on the sequence tree. If these sequences align very
well, there will be few errors in the initial alignments. However, the more distantly
related these sequences, the more errors will be made, and these errors will be propagatedto the multiple sequence alignment. A second problem with the progressive alignment7

method is the choise of suitable scoring matrices and gap penalties that apply to the set ofsequences.

Getting the data into ClustalX
Start ClustalX, and you will see a window that looks something like the one below.

Pull down the File-menu, and choose Load Sequences menu item. Navigate to the folder(subdirectory) that contains the input file (text-file containing the sequences in FastAformat), and choose that file.

8

The left pane (in the figure above) lists the sequences according to the name that follows“>” symbol in the input file. The right pane shows the beginning of each sequence. You
can scroll to the right to see the rest of each sequence by using the scroll bar at the bottomof the pane.

Setting up the alignment parameters
The alignment is done is several succeeding steps: (from Clustal documentation)
1. Reset All Gaps (Alignment->Alignment parameters, Edit->Remove all Gaps)
2. Refine Pairwise Alignment Parameters (Alignment->Alignment parameters)
3. Refine Multiple Alignment Parameters (Alignment->Alignment parameters)
4. Refine Output Format Options (Alignment->Output Format Options)
5. Write Alignment as Postscript (File->Write Alignment as Postscript)
6. Assess the quality of the alignmenta. Not satisfied -> Go to step 1.
b. Satisfied -> Refine the alignment by hand
Pairwise alignment parameters
In order to create the pairwise alignment, ClustalX needs to know what penalties toassign for the creation of a gap and for the extension of that gap. Choose Pairwise
Alignment Parameters from the Alignment-menu. You will see a dialog box like the one
below.

The first choise, Pairwise Alignments, allows you to choose between Slow-Accurate andFast-Approximate methods. The Slow-method is preferred, but if you are aligning somany sequences or the sequences are so long that the program takes a long time to run,9

you may want to use the Fast-method. The Fast-method uses a k-tuple method for
pairwise alignment, whereas Slow-method uses a full dynamic programming algorith.
The box shows the default values for Gap Opening and Gap Extension. Decreasing the
gap penalties will allow the introduction of more gaps, and less mismatches. This may
result is matches that do not reflect homology (identity by descent). Increasing gap
penalties wil have an opposite effect, but may result in missing matches that actually arehomologies.
Weight matrix parameters can be changed too. The IUB DNA weight matrix scoresmatches as 1.9 and mismatches as 0, except that it scores all X’s and N’s as matches to
any IUB ambiguity symbols. The Protein Weight Matrices are equivalent to the same
matrices used as evolutionary models in the production of the dendrogram. All thematrices have their strenghts and down-sides: PAM has been used for years, but is now
somewhat outdated, and the Gonnet can be more appropriate for your purposes.
BLOSUM seems to be best for searching databases.
You can create and load in your own matrix into ClustalX. For the description of the fileformat, take a look at the file matrices.h in the ClustalX-folder:
For amino acids:
char *amino_acid_order = "ABCDEFGHIKLMNPQRSTVWXYZ";
short blosum30mt[]={4,0, 5,-3, -2, 17,0, 5, -3, 9,0, 0, 1, 1, 6,-2, -3, -3, -5, -4, 10,0, 0, -4, -1, -2, -3, 8,-2, -2, -5, -2, 0, -3, -3, 14,0, -2, -2, -4, -3, 0, -1, -2, 6,
0, 0, -3, 0, 2, -1, -1, -2, -2, 4,-1, -1, 0, -1, -1, 2, -2, -1, 2, -2, 4,
1, -2, -2, -3, -1, -2, -2, 2, 1, 2, 2, 6,
0, 4, -1, 1, -1, -1, 0, -1, 0, 0, -2, 0, 8,-1, -2, -3, -1, 1, -4, -1, 1, -3, 1, -3, -4, -3, 11,
1, -1, -2, -1, 2, -3, -2, 0, -2, 0, -2, -1, -1, 0, 8,-1, -2, -2, -1, -1, -1, -2, -1, -3, 1, -2, 0, -2, -1, 3, 8,
1, 0, -2, 0, 0, -1, 0, -1, -1, 0, -2, -2, 0, -1, -1, -1, 4,
1, 0, -2, -1, -2, -2, -2, -2, 0, -1, 0, 0, 1, 0, 0, -3, 2, 5,
1, -2, -2, -2, -3, 1, -3, -3, 4, -2, 1, 0, -2, -4, -3, -1, -1, 1, 5,-5, -5, -2, -4, -1, 1, 1, -5, -3, -2, -2, -3, -7, -3, -1, 0, -3, -5, -3, 20,
0, -1, -2, -1, -1, -1, -1, -1, 0, 0, 0, 0, 0, -1, 0, -1, 0, 0, 0, -2, -1,-4, -3, -6, -1, -2, 3, -3, 0, -1, -1, 3, -1, -4, -2, -1, 0, -2, -1, 1, 5, -1, 9,0, 0, 0, 0, 5, -4, -2, 0, -3, 1, -1, -1, -1, 0, 4, 0, -1, -1, -3, -1, 0,2,4};/*

10

For the DNA:char *nucleic_acid_order = "ABCDGHKMNRSTUVWXY";
short clustalvdnamt[]={
10,
0, 0,
0, 0, 10,0, 0, 0, 0,
0, 0, 0, 0, 10,0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0,

0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,

0,
0,
0,
0,
0,
0,
0,
0,
0,
0,

0,
0,
0,
0,
0,
0,
0,
0,
0,

0,
0,
0,
0,
0,
0,
0,
0,

0,
0, 10,
0, 0, 10,0, 0, 0,0, 0, 0,0, 0, 0,0, 0, 0,

0,
0,
0,
0,

0,
0,
0,

0,
0,

0};

Multiple alignment parameters
Choose Multiple Alignment Parameters from the Alignment-menu. A new dialog box
will appear.

The pairwise and multiple alignment options are set independently, because Clustal needs
to know both. As have been already discussed, a matrix of pairwise alignments is first
calculated, and on the basis of those distances, a multiple alignment is formed. Using
different settings for these alignment steps gives us more flexibility to affect how thealignment is done.

11Compared to pairwise alignment there are a couple of new settings. Delay Divergent
Sequences determines how different two sequences must be in order for their alignment
to be delayed. This tries to compensate for the bias introduced by progressive alignment
method.
DNA transition weight can be modified. Weight 0 means that transitions are scored asmismatches, and weight 1 mean that transitions are given the same weight astransversions. For distantly related DNA sequences, the weight should be near to zero;for closely related sequences it can be useful to assign a higher score.
You don’t have to choose the individual Weight Matrix any more, because we know how
dissimilar the sequences are by now. ClustalX will automatically choose the mostappropriate matrix inside one matrix series. So, if you changed the matrix series to be
used in the pairwise alignment options, be sure to change it here too.

Alignment output-format
The last thing to be modified before performing the alignment is the output-format. When
ClustalX creates an alignment it writes the aligned sequences into a file. There aredifferent multiple alignment formats, which might be needed depending on what program
you have planned to use for further analyses.
For the phylogenetic construction using Phylip-package, choose the Phylip as an output
format. You should also always remember to write the aligned sequences in the Clustalformat, because it is convenient for both publishing the alignment and refining thealignment in the Notepad. If you plan to publish the sequences, turn the sequencenumbering on.
You can modify the output-format by selecting the Output Format Options menu item
form the Aligment-menu.

12Creating the alignment
Finally, it is time to create the alignment. Choose the Do Complete Alignment under the
Alignment menu.
ClustalX tells you what it is doing, but it usually locks the computer, so do not plan to use
the computer for any other purposes while the alignment is still under construction.
One word of warning, though. ClustalX does not understand spaces in the names of thefolders. Therefore, for example, My Documents, cannot be used in the path.
After the alignment is done, the main window will be updated with the aligned
sequences.

The bases are colored, which makes the assessment of alignment that much easier. The
histogram (or line) below the ruler indicates the degree of similarity. Peaks indicate
positions of high similarity, and valleys positions of low similarity.
The grey line just above the sequences is used to mark strongly conserved positions. The“*” character indicates positions that have been fully conserved.

13

Writing alignment as Postscript
It is possible to use the files we have just created to construct a phylogenetic tree, but thequality and the value of that tree will be no better than the quality of the alignment, andwe have not yet considered quality.
It is also important to understand that no matter how dissimilar the sequences are,
ClustalX will always produce an alignment. The mere existence of the alignment does notmean that the sequences are related. It is up to the user to ensure that the sequences in thedata set are actually homologous and therefore alignable.
The quality of the alignment is easier to check if there exists hard copies of thesequences. You have two possibilities. You might print the ClustalX-format alignment,
which exists in the text-format, and use that, but then you’ll lose the information of thecolors.
The other possibility is to install Ghostscript and Ghostview programs, which allow theuser to manipulate Postscript documents, and print the alignment as postscript, which
includes the colors.
Go to File-emu and select Write Alignment as Postscript. A dialog box opens.

14You have some options to change, but after you are satisfied with them, click OK. Openthe postscript-file in Ghostview. The Ghostview-program might give you some warnings
about the incorrect type of the postscript-file, but ignore them by clicking on the Cancelbutton.

Now you can print this alignment by selecting the printer-button in the left and top cornerof the window.

Assessing the quality of the alignment
In practice, many alignments are produced, and they are compared together. You can startby using the default ClustalX options for pairwise and multiple alignment options. In thenext alignments try lowering and highering the gap options by 50%. Produce, say 10-20
different alignments, and then compare those together. Often you need to try more than
10 different settings in order to find the best alignment. What you also need to keep inmind is that alignment is not an absolute thing. It is a best guess according to somealgorithm used by a computer program or by an experienced human eye. It is necessary
for the user to carefully examine each alignment to see if it makes biological sense.

15

After printing the alignments you need to examine them to see if most of the gaps makesense. If many of the gaps seem to be arbitrary (i.e., you think you could have done betterby eye), then you need to improve the alignment. If there are large regions that arepresent in only one or two sequences, you may need to delete those regions from thealignment. In practice, most of the programs used for phylogenetic tree reconstruction,
will delete all the column containing any gaps from the analysis, so you don’t need tobother.
There are some guidelines on how to assess the quality. First remember, that we want tomaximize similarity, and minimize dissimilarity. Therefore, the number of gaps is one
parameter you should pay attention to. Use the histogram in the bottom of the alignment
and the “*” characters above it to assess the conservation of different areas of thealignment.
It is also biologically unsound to assume that there are many gaps with equal spaces
between them. Usually gaps are clustered, and are more common in certain areas than inother areas. So, look for the number and length of the conserved blocks of columns. If thepattern of the gaps looks like they have been randomly inserted, choose anotheralignment. This is, of course, assuming that the sequences are relatively closely related.
If you are aligning an area where there are no functional genes, the above’s all you cando. If you have some knowledge on the functional regions of the sequence you arealigning, you can use this information when assessing the quality of the alignment.
The functional regions are often more or less conserved between the relatively closely
related sequences. Therefore, quite a few gaps should be inserted into those areas, andmost of the gaps should be inserted into less well conserved areas, for example, in thespacer regions between alfa-helixes.
Although it is very time consuming, attempting to improve the alignment through thisprocess of examination and modification of penalties is probably the single mostimportant thing you can do to ensure a high-quality alignment and make a high-quality
phylogeny estimation possible.

Advanced alignment strategies
If you have very difficult sequences to align, you can try iterative alignment procedure inorder to get a better estimate of the real alignment. First, produce an initial alignment
with some quite closely fitting parameter values. Then, produce a new alignment fromthis initial alignment without removing gaps before this second alignment. You caniterate the alignment using the same settings, but doing the alignment based on theprevious alignment multiple times. Sooner or later the alignment will stabilize, and will
not change anymore with the same parameters. This is the best, “iterated”, alignment for
those settings.

16

Normally, it is important to reset the gaps before producing the alignment with new
settings, but this is not done with iterative alignment.
You can also realign only a part of the sequences. Hold down the left mouse button, andpaint a selection. Then, from the Alignment menu select Realign Selected Residue
Range. ClustalX will then do the alignment using the current setting only for the selected
residues. You can also produce a new alignment for selected sequences (Realign Selected
Sequences). Sequences can be selected by holding down the left mouse-button, and thendragging downwards in the sequence name list.

Advanced options
Do alignment from the guide tree
If you have some data on the relationships of the sequences, you can construct a tree in
the Newick-format, and use that for producing a multiple sequence alignment.
Produce a tree like the one below:((
Pan_verus1:0.02428,
Pan_verus2:0.01474):0.03203,(
Pan_velle1:0.00437,
Pan_velle2:0.00579):0.01402,(
Pan_trog1:0.00306,
Pan_trog2:0.00306):0.05015);
Save the tree in a file in text-format.
In Clustal, select the Do Alignment From Guide Tree from the Alignment menu. Thisway you can try to get around the difficulties of the progressive alignment, which might
create wrong alignments, if the sequences are very divergent. This can also be used to
combine morphological data into the sequence alignment step: the knowledge of therelationships of the taxons can be used to guide the alignment process.

Profile alignment
Profile alignment is used for a couple of purposes, but we first discuss how to align a new
sequence into an existing alignment.

17

There is a pull-down menu on the main window top left-hand corner. From the menuchange to Profile Alignment Mode. The Alignment view window is now split into twoparts. The upper part contains the alignment we just created, and lower is empty. The
upper part is called “profile 1” and the lower part is “profile 2”.
In the File-menu you have the options to load profiles 1 and 2. Now we already have theprofile one available, so we only need to load the profile 2. Let’s do that. The main
window is updated, and look something like the one below.

From the alignment-menu, select first the option “Align Sequences to Profile 1”. Afterthat select “Align Profile 2 to Profile 1”. This will create an alignment file, where all thesequences are together. Note that you should always first align the sequences in the
profile 1 before aligning those (already aligned) sequences to the profile 2!
This is a very handy way to add new sequences into an existing alignment. Otherwise you
would have needed to calculate the initial alignment again, which could have been very
laborous in the case of many or very long sequences.

18

Using secondary structure information in the profile alignment
As has been shortly discussed above the sequence alignment can be guided by thesecondary structure of the protein, if such information is available. Often such alignments
are more biologically plausible than the alignments done “randomly”.
In ClustalX the gap penalties are raised at core alpha helix (A) or beta strand (B)residues. The structure information can be used only in the Profile Alignment Mode.
These gap penalties cannot be used in the multiple alignment mode. There are two ways
to include structure information in Clustal, but here we present only the easier one, which
describes the domain areas of the protein. Then the penalties are adjusted in the ClustalX
dialog box.
First we need to create the input files. In the first input file, which the first sequence of all
the sequences to aligned, a descriptions of the domains (helix or strand) is included. The
second input file contains the rest of the sequences in the FastA-format.
The information about the domains is most easily acquired from the SWISS-PROT
descriptions. Find the relevant information from http://www.ebi.ac.uk/swissprot/, andafter you have acquired the SRS results, click on the Accession Number link on the top of
the page. This will take you to the plain text description.
From the description find the lines starting with two capital letters: ID, FT, SQ, and thesequence. Copy those lines into a text file (i.e., into Notepad) and save the file. It should
now something like the one below.
ID
XRC1_HUMAN
STANDARD;
PRT;
633 AA.
FT
HELIX
315
403
BRCT 1.
FT
HELIX
538
629
BRCT 2.
SQ
SEQUENCE
633 AA; 69525 MW; 30CC2421345ABFC2 CRC64;
MPEIRLRHVV SCSSQDSTHC AENLLKADTY RKWRAAKAGE KTISVVLQLE KEEQIHSVDIGNDGSAFVEV LVGSSAGGAG EQDYEVLLVT SSFMSPSESR SGSNPNRVRM FGPDKLVRAAAEKRWDRVKI VCSQPYSKDS PFGLSFVRFH SPPDKDEAEA PSQKVTVTKL GQFRVKEEDESANSLRPGAL FFSRINKTSP VTASDPAGPS YAAATLQASS AASSASPVSR AIGSTSKPQESPKGKRKLDL NQEEKKTPSK PPAQLSPSVP KRPKLPAPTR TPATAPVPAR AQGAVTGKPRGEGTEPRRPR AGPEELGKIL QGVVVVLSGF QNPFRSELRD KALELGAKYR PDWTRDSTHLICAFANTPKY SQVLGLGGRI VRKEWVLDCH RMRRRLPSRR YLMAGPGSSS EEDEASHSGG
SGDEAPKLPQ KQPQTKTKPT QAAGPSSPQK PPTPEETKAA SPVLQEDIDI EGVQSEGQDNGAEDSGDTED ELRRVAEQKE HRLPPGQEEN GEDPYAGSTD ENTDSEEHQE PPDLPVPELPDFFQGKHFFL YGEFPGDERR KLIRYVTAFN GELEDYMSDR VQFVITAQEW DPSFEEALMDNPSLAFVRPR WIYSCNEKQK LLPHQLYGVV PQAThe ID line gives description of the sequence and what it codes. The FT lines describe
what kind of domains are present in the protein. Those should say either HELIX or
STRAND (always double-check those; they might be inaccurate). The SQ line gives
molecular weight and some other information of the succeeding amino acid sequence.

19

For
checkingthesecondarystructures,gotohttp://www.emblheidelberg.de/predictprotein/submit_def.html and paste in the first protein sequence. In a
short while the results will be emailed to you. From the results, you’ll find a description:AA|MPEIRLRHVVSCSSQDSTHCAENLLKADTYRKWRAAKAGEKTISVVLQLEKEEQIHSVDI|
PHD sec | EEEEEEEEEE
HHHHHHHHH HHHHHHHHHHH
EEEEEE
EEEEE |
Rel sec |993678997772578764999998651136878999946883699885235453354451|
detail:prH sec |000000000000000116899988764467888899962100000000001111000000|
prE sec |006778898875210000000000000000000000000003799886431212566664|
prL sec |993210001114688872000001225432111000027886200012557665322225|
subset: SUB sec |LL.EEEEEEEE.LLLLL.HHHHHHHH...HHHHHHHH.LLL.EEEEEE..L.L..E..E.|
accessibility
3st:
P_3 acc | eebebebbbbbbeeebeebbeebbebee ebebbeeeeebbbbbbebeeeeebbbbeb|
10st:
PHD acc |397060600000099707600770070774570600777770000006067776000060|
Rel acc |002325036846201120058314433100121164412342639850325320404504|
subset: SUB acc |.....b..bbbb.......bb..bb.........bbe...e.b.bbb...e...b.bb.b|

The line marked with AA gives the original sequence, and the the next line, starting with
PHD sec gives the predicted secondary structures. Rel sec gives the reliability of thesecondary strusture prediction. H mean helix, and E mean sheet. You can use thisinformation for the description of the structures for ClustalX input.
You have just created the first input file. The second file should include the othersequences you’re interested in in FastA-format (see above).
After preparing these input files, go to ClustalX, and switch to Profile Alignment Mode.
From the File menu select Load Profile 1, and search for the first input file. If ClustalX
recognizes the file to contain the weights for the gaps it asks you whether to use thepenalties or not.

If you have formatted the files as described above, but ClustalX does not recognize theweights, go to Alignment->Alignment Parameters->Secondary Structure parameters.
From the opening dialog box turn the Use Profile Secondary Structure option on (yes).
After that try to load the first input file again.

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If the loading was successful, go to Alignment->Alignment Parameters->Secondary
Structure parameters. A dialog box opens.

In the first input file you have set up the areas of protein consisting of helixes and strands.
In the box you can set the gap penalties for these areas. The penalties are multiples of thenormal penalty given by the Multiple Sequence Alignment Parameters.
After setting up the parameters, load in the second Profile (File->Load Profile 2). The
alignment is then done in two phases as previously described: First align sequences to the
profile 1, and then align profile 2 to profile 1.
A new multiple alignment is created, and the gaps are more often inserted into the areas
outside the described secondary structures than within them, depending on theparameters.

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