POSTERS - BLAST X - University of Utah

BLAST X Wed. Morning Session
INVESTIGATING THE STRUCTURE OF TERNARY COMPLEX OF HISTIDINE KINASE CheA,
COUPLING PROTEIN CheW, AND CHEMORECEPTOR BY PULSED DIPOLAR ESR
SPECTROSCOPY
Jaya Bhatnagar, Peter P. Borbat, Jack H. Freed, Brian R. Crane
Cornell University, B 150 Caldwell Hall, Ithaca, NY 14853
A central question in understanding the mechanism of chemotaxis involves the nature of
interactions between histidine kinase CheA, adaptor protein CheW and receptors. Pulsed
dipolar ESR spectroscopy (PDS) has developed as a valuable technique for structural
characterization of protein complexes. PDS provides long-range distance information between
spin-labeled residues in the proteins. A set of distance measurements can be subsequently
used to model the assembly structure of the whole complex. In our previous work, we
demonstrated the success of this approach in predicting the structure of complex of CheW with
CheA. We have now applied PDS to the ternary complex formed by CheA, CheW and soluble
chemoreceptor fragments. Our results indicate changes in distance distributions from spinlabeled
sites on P4, P5 domains and CheW in the presence of unlabeled receptor. Dipolar
signals between spin-labeled receptor and CheA∆289 (domains P3, P4 and P5 together) or
CheW provide important insights about the relative position and orientation of the three
components with respect to each other. Based on this data we have developed a structural
model of the ternary complex and the conformational changes CheA undergoes upon binding to
receptor.
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