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PDBsum entry 3g6b
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Signaling protein
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PDB id
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3g6b
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References listed in PDB file
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Key reference
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Title
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The structure of a soluble chemoreceptor suggests a mechanism for propagating conformational signals.
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Authors
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A.M.Pollard,
A.M.Bilwes,
B.R.Crane.
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Ref.
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Biochemistry, 2009,
48,
1936-1944.
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PubMed id
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Abstract
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Transmembrane chemoreceptors, also known as methyl-accepting chemotaxis proteins
(MCPs), translate extracellular signals into intracellular responses in the
bacterial chemotaxis system. MCP ligand binding domains control the activity of
the CheA kinase, situated approximately 200 A away, across the cytoplasmic
membrane. The 2.17 A resolution crystal structure of a Thermotoga maritima
soluble receptor (Tm14) reveals distortions in its dimeric four-helix bundle
that provide insight into the conformational states available to MCPs for
propagating signals. A bulge in one helix generates asymmetry between subunits
that displaces the kinase-interacting tip, which resides more than 100 A away.
The maximum bundle distortion maps to the adaptation region of transmembrane
MCPs where reversible methylation of acidic residues tunes receptor activity.
Minor alterations in coiled-coil packing geometry translate the bulge distortion
to a >25 A movement of the tip relative to the bundle stalks. 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 interacts with
the CheA kinase.
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