Laboratory of CryoEM Structural Biology
Institute for Protein Research
Professor

Takayuki KATO

tkato

Assistant Professor

Hiroko TAKASAKI

takahiro

Assistant Professor

Jun-ichi KISHIKAWA

kishi.jun

URL:http://www.protein.osaka-u.ac.jp/cryoem/
A protein is one long biopolymer
consisting of 20 different aminoacids joined by peptide bonds.
According to a program called
amino acid sequence, proteins
spontaneously assume a fixed
three-dimensional structure and act
as sensors, motors, or othermachines that can perform almost
any function imaginable by humans.
In order to elucidate how thesenano-sized molecular machines
adopt their three-dimensional
structures and what mechanisms
are responsible for their functions,
we are performing structural
analysis using cryo-electron
emission microscopy (cryo-EM).

Development of cryo-electron
microscopy and analysis methods
In the past, the low resolution of
cryo-EMs made it impossible toconstruct atomic model molecules on
their own. However, with the adventof new electron microscope cameras
developed in the 20131990s, structuresof large complexes and membraneproteins that could not be analyzed byother methods can now be analyzed at
atomic resolution. As a result, cryoEMs are now used first and foremost
for proteins that would otherwise bedifficult to crystallize. Despite therapid development of cryo-EM, there
are still many problems to be solved.
It is still developing and still has a lotof potential. We are developing
imaging and analysis methods tomaximize their potential.

Analysis of the operating
mechanism of molecular motors

Fig. Structure of 1flagellar hook
The flagellum is in a bent state, and cryo-EM is the only techniquethat can analyze the structure of the flagellum in this bent state.

Proteins flexibly and repeatedly undergo
conformational changes in vivo to performtheir functions. Flagellar motors and ATPases,
which are rotating molecular motors, areexamples of such proteins. In order toelucidate this mechanism, it is necessary tocapture the conformational changes of thesemolecular motors while they are in motion.
Cryo-EM allows us to take images of various
structural states and visualize the motion byconnecting them. In this way, the mechanism
can be clarified from the structural analysis of
the functional state.
Structural analysis of olfactory
receptors
Humans are able to sense tens of thousandsof odors through the use of some 400 different
olfactory receptors. These olfactory receptors
are seven transmembrane proteins belonging
to the G protein-coupled receptor (GPCR)
family. There are few examples of structural
analysis of the binding of volatile odor
molecules to these olfactory receptors, andmost results are based on calculations of how
odor molecules are recognized and bound.
Therefore, cryo-EM is used to analyze thestructure of the odor molecule binding state.

Fig. 2 Cryo-electron microscope owned by the Institute for Protein Research
The Institute for Protein Research has one of the world's best cryo-electron microscopes and one
electron microscope for screening, providing a smooth environment for protein structure analysis.

It is a privilege to be a

student to experience thejoy of learning andInstitute for Protein Research, Osaka University
3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
TEL&FAX: +81-6-6105-6079

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