"DNA-->mRNA-->Protein", this is a scheme of gene expression,
so-called "Central Dogma" in molecular biology. However, the
product here is a polypeptide in which amino acids are polymerized, not
a functional protein. To get a mature protein, the polypeptide had to undergo
several steps including modifications, foldings and so on. Moreover, proteins
must be transported to the places where they actually function. Proteins
are usually synthesized in cytosol, however, many of them function outside
cytosol, especially outside cells and in the biomembranes. These proteins
had to be translocated across or integrated into cellular membranes. Since
the biomembranes (especially the plasma membranes) are the barrier between
outside and inside the cells, the traverse of materials through the membranes
is strictly restricted. For example, the small molecules such as ions and
sugars, and even the water molecules are not allowed freely to translocate
across the membranes. Therefore, some tactical mechanisms are required
to translocate across and integrated into the biomembranes. The figure
illustrates how membrane proteins are integrated into the ER membrane of
eukaryotic cells (lower) and cytoplasmic membranes of bacterial cells (upper).
While the precise names of the factor involved in the reactions are slightly
different, the fundamental flows of the reactions are remarkably similar.
Our purpose of the research is to clarify the detailed molecular mechanisms
of the life phenomena that are conserved among all of the living things,
by means of E. coli, a model organism. It is also used to be known that
protein translocation across and integration into membranes are cold-sensitive
processes. For these, our research is one of the most important projects
to clarify the relationship between "temperature and life
phenomena", a major purpose of the CRC Institute. We have
succeeded in purification of factors involved in protein translocation
and integration, and reconstitution of the reactions by means of the purified
factors in vitro. During the processes, we have identified a novel glycolipid
essential for protein integration. Although this factor is not proteinaceous,
we have named it MPIase (Membrane Protein Integrase) after its enzyme-like
function. We are now investigating the relationship between the structure
and function of MPIase. We expect that plants and animals express an MPIase
homolog because the mechanisms underlying protein integration into membranes
are quite similar among all the living things. Especially, it is known
that the mechanisms of protein transport in chloroplasts are quite similar
to those in E. coli. These indicate that it is expected that modification
of the chloroplast MPIase allows development of the cold-resistant plants.
What's new? -
-2018.4 Our paper was published in J. Biochem.
-2017.4 Our paper was published in Biochem. Biophys. Res. Commun.
-2016.12 Our paper was published in Gene. Cells
-2015.12 Our review article was published in Med. Res. Arch.
-2014.11 Our review article was published in Biomol. Concepts
-2014.5 Our collaboration with Prof Nureki (Tokyo Univ) was published in Nature
-2013.6 Our paper was published in Proc. Natl. Acad. Sci. USA
-2012.12. Our paper was published in Nature Communications
-2010.1 Lab opened
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