| RESEARCH SUMMARY: Our lab studies tertiary
structures of biological macromolecules mainly by X-ray crystallography
to understand mechanisms of activities of these intricate
3D machineries.
One of our main focuses is recombination mediators (RMs),
ubiquitous proteins important for DNA recombination, replication
and repair in all organisms. Eukaryotic RMs include such proteins
as BRCA2 and Rad52. Mechanisms of RM activities are poorly
understood. RecF, RecO and RecR (RecFOR) proteins represent
one of the major groups of prokaryotic RMs. They are involved
in diverse processes, including SOS response, repair of stalled
replication forks, of ssDNA gaps, and, under certain conditions,
of dsDNA breaks. Mechanisms by which RecFOR recognizes specific
DNA sites and interacts with other protein partners are not
known.
Recently we deciphered crystal structures of RecO, RecF and
RecR proteins. Multidomain architecture of RecO is suitable
for multiple interactions with different DNA substrates and
various protein partners. Like BRCA2, it possesses an OB-fold
domain which is involved in DNA binding and protein interactions.
The tetrameric structure of RecR surprisingly resembles DNA
clamp molecules. The role of DNA clamp in RecFOR function
is not clear. We crystallized RecF protein as well and are
conducting solution studies of RecF interactions with DNA
and protein partners. RecF structure is surprisingly similar
to the head domain structure of eukaryotic Rad50, a major
player of DNA repair machinery. Based on the analysis of ABC-type
ATPase features of RecF and its similarity with Rad50 we proposed
a model of RecF dimer binding to DNA and of a potential mechanism
of DNA damage site recognition. Structural studies are followed
by solution studies of RecF DNA binding and interaction with
RecR.
Overall, structural and functional studies demonstrate that
each of RecFOR proteins resemble specific domains of eukaryotic
RMs and thus provide a convenient model system to study the
basic mechanisms of recombination mediators.
Figure 1: Structure of RecO from D. radiodurans
Figure 2: The structure of RecF protein from
Deinococcus radiodurans.
In collaboration with other laboratories at SLU and Washington
University in St. Louis we perform structural studies of other
proteins involved in DNA repair and replication, transcription
regulation and other cellular processes.
Our protein crystallography facility includes High-Throughput
HomeLab system which consists of a new X-ray generator Rigaku
MicroMax-007, Raxis IV++ image plate detector, the Confocal
Blue optics and X-stream 2000 cryo-cooling system, and numerous
computers including a SGI Octane, PC Linux and Windows graphic
workstations.
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