bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interdomain Communications in Bifunctional Enzymes: How Are Different Activities Coordinated?
Authors: Nagradova Natalya 
Published: November 2003

AbstractAlthough bifunctional enzymes containing two different active centers located within separate domains are quite common in living systems, the significance of this bifunctionality is not always clear, and the molecular mechanisms of site‐site interactions in such complex systems have come under the scrutiny of science only in recent years. This review summarizes recent data on the mechanisms of communication between active centers in bifunctional enzymes. Three types of enzymes are considered: (1) those catalyzing consecutive reactions of a metabolic pathway and exhibiting substrate channeling (glutamate synthase and imidazole glycerol phosphate synthase), (2) those catalyzing consecutive reactions without substrate channeling (lysine‐ketoglutarate reductase/saccharopine dehydrogenase), and (3) those catalyzing opposed reactions (6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase). The functional role of interdomain communications is briefly discussed. IUBMB Life, 55: 459‐466, 2003
Telomere Higher‐Order Structure and Genomic Instability
Authors: Fletcher Terace 
Published: November 2003

AbstractTelomeres, nucleoprotein complexes at the end of eukaryotic chromosomes, have vital roles in chromosome integrity. Telomere chromatin structure is both intricate and dynamic allowing for a variety of responses to several stimuli. A critical determinant in telomere structure is the G‐strand overhang. Facilitated by telomeric proteins, the G‐strand overhang stabilizes telomere higher‐order assemblies most likely by adopting unusual DNA structures. These structures influence activities that occur at the chromosome end. Dysfunctional telomeres induce signals resulting in cell growth arrest or death. To overcome telomere dysfunction, cancer cells activate the DNA polymerase, telomerase. The presence of telomerase at the telomere may establish a particular telomeric state. If the chromosome ends of cancer and normal cells exist in different states, cancer‐specific telomere structures would offer a unique chemotherapeutic target. IUBMB Life, 55: 443‐449, 2003
The Role of DNA Recombination in Herpes Simplex Virus DNA Replication
Authors: Wilkinson Dianna , Weller Sandra 
Published: November 2003

AbstractIn many organisms the processes of DNA replication and recombination are closely linked. For instance, in bacterial and eukaryotic systems, replication forks can become stalled or damaged, in many cases leading to the formation of double stranded breaks. Replication restart is an essential mechanism in which the recombination and repair machinery can be used to continue replication after such a catastrophic event. DNA viruses of bacteria such as lambda and T4 also rely heavily on DNA recombination to replicate their genomes and both viruses encode specialized gene products which are required for recombination‐dependent replication. In this review, we examine the linkage between replication and recombination in the eukaryotic pathogen, Herpes Simplex Virus Type 1 (HSV‐1). The evidence that recombination plays an intrinsic role in HSV‐1 DNA replication and the infection process will be reviewed. We have recently demonstrated that HSV‐1 encodes two proteins which may be analogous to the lambda phage recombination system, Red αand β. The HSV‐1 alkaline nuclease, a 5' to 3' exonuclease, and ICP8, a single stranded DNA binding protein, can carry out strand annealing reactions similar to those carried out by the lambda Red system. In addition, evidence suggesting that host recombination proteins may also be important for HSV‐1 replication will be reviewed. In summary, it is likely that HSV‐1 infection will require both viral and cellular proteins which participate in various pathways of recombination and that recombination‐dependent replication is essential for the efficient replication of viral genomes. IUBMB Life, 55: 451‐458, 2003
Genomic Location and Variation of the Gene for CRS, a Complement Binding Protein in the M57 Strains ofStreptococcus pyogenes
Authors: Binks Michael , McMillan David , Sriprakash Kadaba S. 
Published: November 2003

ABSTRACTAll isolates of serotype M1 of group A streptococci possess a gene for streptococcal inhibitor of complement (SIC) in themgaregulon, which harbors genes for other virulence factors, such as M and M-like proteins, C5a peptidase, and a regulator. In serotype M57 the gene for a protein that is closely related to SIC (crs57) is located outside themgaregulon. We mapped the location of thecrs57gene in six strains ofemm57(gene encoding the M57 protein) sequence types to an intergenic region between the ABC transporter gene (SPy0778) and the gene for a small ribosomal protein (rpsU). The noncoding sequences on both sides ofcrs57exhibited high degrees of identity to the corresponding regions ofsicfrom M1 strains. This included one of the inverted repeat sequences of IS1562but not the insertion element itself. These observations suggest thatcrs57was recently acquired by serotype M57 or its progenitor via horizontal acquisition from serotype M1. The sixemm57sequence type isolates analyzed in this study belong to two distinct molecular types (vir types VT8 and VT101). Although thecrs57sequences from VT8 strains had very few substitution mutations, the VT101crs57sequence had a large number of such mutations. The CRS57 proteins from these strains are secretory products and have the ability to bind to complement proteins. All these proteins contain several tryptophan-rich repeats designated DWS motifs and internal repeat sequences. In all of these structural and biochemical characteristics CRS57 resembles SIC from M1 strains. Hence, CRS57 has a functional role similar to that of SIC in an M1 strain.
SalivaryAntibodies Directed against Outer Membrane Proteins of
Moraxella catarrhalis
in HealthyAdults
Authors: Stutzmann Meier Patricia , Heiniger Nadja , Troller Rolf , Aebi Christoph 
Published: November 2003

ABSTRACT

Moraxella
catarrhalis
is a major mucosal pathogen of the human
respiratory tract, but the mucosal immune response directed against
surface components of this organism has not been characterized in
detail. The aim of this study was to investigate the salivary
immunoglobulin A (IgA) response toward outer membrane proteins (OMP) of
M. catarrhalis
in healthy adults, the group of
individuals least likely to be colonized and thus most likely to
display mucosal immunity. Unstimulated saliva samples collected from 14
healthy adult volunteers were subjected to IgA immunoblot analysis with
OMP preparations of
M. catarrhalis
strain O35E.
Immunoblot analysis revealed a consistent pattern of IgA reactivity,
with the appearance of five major bands located at >250, 200,
120, 80, and 60 kDa. Eleven (79%) of 14 saliva samples elicited
reactivity to all five bands. Immunoblot analysis with a set of
isogenic knockout mutants lacking the expression of individual OMP was
used to determine the identities of OMP giving rise to IgA bands. Human
saliva was shown consistently to exhibit IgA-binding activity for
oligomeric UspA2 (>250 kDa), hemagglutinin (200 kDa), monomeric
UspA1 (120 kDa), transferrin-binding protein B (TbpB), monomeric UspA2,
CopB, and presumably OMP CD. TbpB, oligomeric UspA2, and CopB formed a
cluster of bands at about 80 kDa. These data indicate that the human
salivary IgA response is directed consistently against a small number
of major OMP, some of which are presently considered vaccine
candidates. The functional properties of these mucosal antibodies
remain to be
elucidated.
Specificity and Mechanism of Immunoglobulin M (IgM)-and IgG-Dependent Protective Immunity to LarvalStrongyloides stercoralisinMice
Authors: Ligas Jessica A. , Kerepesi Laura A. , Galioto Ann Marie , Lustigman Sara , Nolan Thomas J. , Schad Gerhard A. , Abraham David 
Published: November 2003

ABSTRACTProtective immunity in mice to the infective third-stage larvae (L3) ofStrongyloides stercoraliswas shown to be dependent on immunoglobulin M (IgM), complement activation, and granulocytes. The objectives of the present study were to determine whether IgG was also a protective antibody isotype and to define the specificity and the mechanism by which IgG functions. Purified IgG recovered from mice 3 weeks after a booster immunization with live L3 was shown to transfer high levels of protective immunity to naïve mice. IgG transferred into mice treated to block complement activation or to eliminate granulocytes failed to kill the challenge larvae. Transfer of immune IgG into IL-5 knockout (KO) mice, which are deficient in eosinophils, resulted in larval attrition, while transfer into FcRγ KO mice did not result in larval killing. These findings suggest that IgG from mice immunized with live L3 requires complement activation and neutrophils for killing of L3 through an antibody-dependent cellular cytotoxicity (ADCC) mechanism. This is in contrast to the results of investigations using IgM from mice immunized with live L3 and IgG from mice immunized with larval antigens soluble in deoxycholate in which protective immunity was shown to be ADCC independent. Western blot analyses with immune IgM and IgG identified few antigens recognized by all protective antibody isotypes. Results from immunoelectron microscopy demonstrated that the protective antibodies bound to different regions in the L3. It was therefore concluded that while IgM and IgG antibodies are both protective against larvalS. stercoralis, they recognize different antigens and utilize different killing mechanisms.
Intestinal Antilectin Immunoglobulin A AntibodyResponse and Immunity to
Entamoeba dispar
Infection followingCure of Amebic LiverAbscess
Authors: Ravdin Jonathan I. , Abd-Alla Mohamed D. , Welles Seth L. , Reddy Selvan , Jackson Terry F. H. G. 
Published: November 2003

ABSTRACT

We
followed 93 subjects with amebic liver abscess (ALA) and 963 close
associate controls at 3-month intervals for 36 months to characterize
intestinal and humoral antibody responses to the amebic
galactose-inhibitable lectin and to determine whether immunity
developed to
Entamoeba histolytica
or
Entamoeba
dispar
infection following cure of ALA. We found that ALA subjects
had a higher prevalence and level of intestinal antilectin
immunoglobulin A (IgA) and serum anti-LC3 (cysteine-rich recombinant
lectin protein) IgA and IgG antibodies,
P
< 0.01 and
P
< 0.05, respectively, compared to controls. The
intestinal antilectin IgA antibody response was sustained over a longer
time period in ALA subjects (71.8% remained positive at 18
months and 52.6% at 36 months,
P
< 0.001
compared to 17.6% and 10.3% of controls, respectively).
ALA subjects were highly immune to
E. dispar
infection
throughout the study (0% infected at 6 and 36 months, compared
to 6.5% and 4.9% of control subjects, respectively,
P
< 0.05). Upon entry into the study, 6.3% of
ALA subjects were infected with
E. histolytica;
the incidence
of new
E. histolytica
infections in controls (as determined by
culture) was too low (1.4%) to determine whether ALA subjects
exhibited immunity to new infections. We found that stool cultures
every 3 months markedly underestimated the occurrence of new
E.
histolytica
infections, as 15.3% of controls seroconverted
after 12 months of follow-up. Unfortunately, under the field conditions
present in Durban, South Africa, enzyme-linked immunosorbent assay for
detection of lectin antigen in stool yielded unreliable results. In
summary, subjects cured of ALA exhibited sustained mucosal IgA antibody
responses to the amebic galactose-inhibitable lectin and a high level
of immunity to
E. dispar
infection. Determination of immunity
to
E. histolytica
following cure of ALA will require the use
of more sensitive and reliable diagnostic
methods.
Cloning and Expression of the Major SecretedCathepsin B-Like Protein from Juvenile
Fasciola hepatica
andAnalysis of Immunogenicity following Liver FlukeInfection
Authors: Law Ruby H. P. , Smooker Peter M. , Irving James A. , Piedrafita David , Ponting Rebecca , Kennedy Nicholas J. , Whisstock James C. , Pike Robert N. , Spithill Terry W. 
Published: November 2003

ABSTRACT

The
functions of the cathepsin B-like proteases in liver flukes are unknown
and analysis has been hindered by a lack of protein for study, since
the protein is produced in small amounts by juvenile flukes. To
circumvent this, we isolated and characterized a cDNA encoding the
major secreted cathepsin B from
Fasciola hepatica
. The
predicted preproprotein is 339 amino acids in length, with the mature
protease predicted to be 254 amino acids long, and shows significant
similarity to parasite and mammalian cathepsin B. Only one of the two
conserved histidine residues required for cathepsin B exopeptidase
activity is predicted to be present. Recombinant preproprotein was
produced in yeast, and it was shown that the recombinant proprotein can
undergo a degree of self-processing in vitro to the mature form, which
is active against gelatin and synthetic peptide substrates. The
recombinant protein is antigenic in vaccinated rats, and antibodies to
the protein are detected early after infection of rats and sheep with
F. hepatica
. The kinetics of the response to cathepsin B and
cathepsin L after infection of sheep and rats confirm the temporal
expression of these proteins during the life cycle of the
parasite.
Temporal Analysis of
Borrelia burgdorferi
Erp Protein Expression throughout the Mammal-Tick InfectiousCycle
Authors: Miller Jennifer C. , von Lackum Kate , Babb Kelly , McAlister Jason D. , Stevenson Brian 
Published: November 2003

ABSTRACT

Previous
immunological studies indicated that the Lyme disease spirochete,
Borrelia burgdorferi
, expresses Erp outer surface proteins
during mammalian infection. We conducted analyses of Erp expression
throughout the entire tick-mammal infectious cycle, which revealed that
the bacteria regulate Erp production in vivo. Bacteria within unfed
nymphal ticks expressed little to no Erp proteins. However, as infected
ticks fed on mice,
B. burgdorferi
increased production of Erp
proteins, with essentially all transmitted bacteria expressing these
proteins. Mice infected with
B. burgdorferi
mounted rapid IgM
responses to all tested Erp proteins, followed by strong immunoglobulin
G responses that generally increased in intensity throughout 11 months
of infection, suggesting continued exposure of Erp proteins to the host
immune system throughout chronic infection. As naive tick larvae
acquired
B. burgdorferi
by feeding on infected mice,
essentially all transmitted bacteria produced Erp proteins, also
suggestive of continual Erp expression during mammalian infection.
Shortly after the larvae acquired bacteria, Erp production was
drastically downregulated. The expression of Erp proteins on
B.
burgdorferi
throughout mammalian infection is consistent with
their hypothesized function as factor H-binding proteins that protect
the bacteria from host innate immune
responses.
Role of Receptor Proteins for Enterobactin and 2,3-Dihydroxybenzoylserine in Virulence of
Salmonella enterica
Authors: Rabsch W. , Methner U. , Voigt W. , Tschäpe H. , Reissbrodt R. , Williams P. H. 
Published: November 2003

ABSTRACT

Single, double, and triple mutants of an enterobactin-deficient mutant strain of
Salmonella enterica
serovar Typhimurium were constructed that were defective in the expression of the iron-regulated outer membrane proteins (IROMPs) FepA, IroN, and Cir, which are proposed to function as catecholate receptors. Uptake of naturally occurring and chemically synthesized catecholate molecules by these mutants was assessed in standard growth promotion assays. Unique patterns of uptake were identified for each IROMP; specifically, FepA and IroN were confirmed to be required for transport of enterobactin, and all three proteins were shown to function as receptors for the enterobactin breakdown product 2,3-dihydroxybenzoylserine. The
fepA
,
iroN
, and
cir
alleles were transduced to enterobactin-proficient strains of
S. enterica
serovar Typhimurium and
S. enterica
serovar Enteritidis, and the resulting phenotypes were confirmed by analysis of outer membrane protein profiles, by sensitivity to KP-736, a catecholate-cephalosporin conjugate, and by growth promotion tests on egg white agar. Intragastric infections of mice with the
S. enterica
serovar Typhimurium strains indicated that the parental strain and the
fepA iroN
double mutant were similarly virulent but that the
fepA iroN cir
triple mutant was significantly attenuated. Moreover, in mixed infections, the
fepA iroN
mutant showed similar cecal colonization and invasion of the liver to the parental strain, while the triple mutant showed significantly reduced cecal colonization and no measurable spread to the liver. Infections of 4-day-old chicks with
S. enterica
serovar Enteritidis strains also indicated that mutation of the
fepA iroN
genes did not significantly reduce cecal colonization and systemic spread compared with those of the parental strain. The results indicate that, while enterobactin uptake is not essential for the virulence of
S. enterica
serovars in mouse and chicken infection models, the ability to take up 2,3-dihydroxybenzoylserine via any of the three catecholate siderophore receptors appears to play an important role, since the
S. enterica
serovar Typhimurium triple mutant was significantly attenuated in the mouse model. Salmochelins appear not to be involved in the virulence of
S. enterica
.
A Humoral Immune Response Confers Protection againstHaemophilus ducreyiInfection
Authors: Cole Leah E. , Toffer Kristen L. , Fulcher Robert A. , San Mateo Lani R. , Orndorff Paul E. , Kawula Thomas H. 
Published: November 2003

ABSTRACTHaemophilus ducreyiis the etiologic agent of the sexually transmitted genital ulcer disease chancroid. Neither naturally occurring chancroid nor experimental infection withH. ducreyiresults in protective immunity. Likewise, a single inoculation ofH. ducreyidoes not protect pigs against subsequent infection. Accordingly, we used the swine model of chancroid infection to examine the impact of multiple inoculations on a host's immune response. After three successive inoculations withH. ducreyi, pigs developed a modestly protective immune response evidenced by the decreased recovery of viable bacteria from lesions. All lesions biopsied 2 days after the first and second inoculations contained viableH. ducreyicells, yet only 55% of the lesions biopsied 2 days after the third inoculation did. Nearly 90% of the lesions biopsied 7 days after the first inoculation contained viableH. ducreyicells, but this percentage dropped to only 16% after the third inoculation. Between the first and third inoculations, the average recovery of CFU from lesions decreased approximately 100-fold. The reduced recovery of bacteria corresponded directly with a fivefold increase inH. ducreyi-specific antibody titers and the emergence of bactericidal activity. These immune sera were protective when administered to naïve pigs prior to challenge withH. ducreyi. These data suggest that pigs mount an effective humoral immune response toH. ducreyiafter multiple exposures to the organism.
Monoclonal Antibody MG96 Completely Blocks
Plasmodium yoelii
Developmentin
Anophelesstephensi
Authors: Dinglasan Rhoel R. , Fields Iesha , Shahabuddin Mohammed , Azad Abdu F. , Sacci John B. 
Published: November 2003

ABSTRACT

In
spite of research efforts to develop vaccines against the causative
agent of human malaria,
Plasmodium falciparum
, effective
control remains elusive. The predominant vaccine strategy focuses on
targeting parasite blood stages in the vertebrate host. An alternative
approach has been the development of transmission-blocking vaccines
(TBVs). TBVs target antigens on parasite sexual stages that persist
within the insect vector, anopheline mosquitoes, or target mosquito
midgut proteins that are presumed to mediate parasite development. By
blocking parasite development within the insect vector, TBVs
effectively disrupt transmission and the resultant cascade of secondary
infections. Using a mosquito midgut-specific mouse monoclonal antibody
(MG96), we have partially characterized membrane-bound midgut
glycoproteins in
Anopheles gambiae
and
Anopheles
stephensi
. These proteins are present on the microvilli of midgut
epithelial cells in both blood-fed and unfed mosquitoes, suggesting
that the expression of the protein is not induced as a result of blood
feeding. MG96 exhibits a dose-dependent blocking effect against
Plasmodium yoelii
development in
An. stephensi.
We
achieved 100% blocking of parasite development in the mosquito
midgut. Preliminary deglycosylation assays indicate that the epitope
recognized by MG96 is a complex oligosaccharide. Future investigation
of the carbohydrate epitope as well as gene identification should
provide valuable insight into the possible mechanisms of ookinete
attachment and invasion of mosquito midgut epithelial
cells.
Analysis of Virulence and Inflammatory Potential of
Shigella flexneri
Purine Biosynthesis Mutants
Authors: Cersini Antonella , Martino Maria Celeste , Martini Irene , Rossi Giacomo , Bernardini Maria Lina 
Published: November 2003

ABSTRACT

Several
Shigella flexneri
mutants with defects in aromatic amino acid and/or purine biosynthesis have been evaluated as vaccines in humans or in animal models. To be suitable as a vaccine, a mutant has to show virulence attenuation, minimal reactogenicity, and a good immunogenic potential in animal models. With this aim, we have constructed five
S. flexneri
5 (wild-type strain M90T) mutants with inactivation of one or two of the loci
purEK
,
purHD
, and
guaBA
, governing early or late steps of purine biosynthesis. The mutants have been analyzed in vitro in cell cultures and in vivo in the Sereny test and in the murine pulmonary model of shigellosis. M90T
guaBA
, M90T
guaBA purEK
, M90T
guaBA purHD
, and M90T
purHD purEK
gave a negative result in the Sereny test. In contrast, in the murine pulmonary model all of the strains had the same 50% lethal dose as the wild type, except M90T
guaBA purHD
, which did not result in death of the animals. Nevertheless, bacterial counts in infected lungs, immunohistochemistry, and reverse transcription-PCR analysis of mRNAs for tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), interleukin-1β (IL-1β), IL-6, IL-12, and inducible nitric oxide synthase (iNOS) revealed significant differences among the strains. At 72 h postinfection, M90T
guaBA purHD
still induced proinflammatory cytokines and factors such as IL-1β, IL-6, TNF-α, and iNOS, along with cytokines such as IL-12 and IFN-γ. Moreover, in the absence of evident lesions in murine tissues, this mutant highly stimulated major histocompatibility complex class II expression, showing a significant ability to activate the innate immunity of the host.