POSTERS - BLAST X - University of Utah

BLAST X Poster #13
STRUCTURE OF SOLUBLE CHEMORECEPTOR SUGGESTS A MECHANISM FOR
PROPAGATING CONFORMATIONAL SIGNALS
Abiola Pollard and Brian Crane
Cornell University, Chemistry Research Bldg. G63, Ithaca, NY 14853
Transmembrane chemoreceptors, also known as methyl-accepting chemotaxis proteins
(MCP’s), translate extracellular signals into intracellular responses in the bacterial chemotaxis
system. MCP ligand binding domains control the activity of the CheA kinase, situated ~200 Å
away, across the cytoplasmic membrane. The 2.15 Å resolution crystal structure of a T.
maritima soluble receptor (Tm14) reveals distortions in its dimeric four-helix bundle that provide
insight into the conformational states available to MCP’s for propagating signals. A bulge in one
helix generates asymmetry between subunits that displaces the kinase-interacting tip, which
resides over 100 Å away. The maximum bundle distortion maps to the adaptational region of
transmembrane MCP’s where reversible methylation of acidic residues tunes receptor activity.
Minor alterations in coiled-coil packing geometry translates the bulge distortion to a >25 Å
movement of the tip. The Tm14 structure discloses how alterations in local helical structure,
which could be induced by changes in methylation state and/or by conformational signals from
membrane proximal regions, can reposition a remote domain that regulates the CheA kinase.
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