Doebber M, Bordignon E, Klare JP, Holterhues J, Martell S, Mennes N, Li L, Engelhard M, Steinhoff HJ. Salt-driven equilibrium between two conformations in the HAMP domain from Natronomonas pharaonis: the language of signal transfer?
J Biol Chem 2008;
283:28691-701. [PMID:
18697747 PMCID:
PMC2661416 DOI:
10.1074/jbc.m801931200]
[Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Revised: 08/06/2008] [Indexed: 11/06/2022] Open
Abstract
HAMP domains (conserved in histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, and phosphatases) perform their putative function as signal transducing units in diversified environments in a variety of protein families. Here the conformational changes induced by environmental agents, namely salt and temperature, on the structure and function of a HAMP domain of the phototransducer from Natronomonas pharaonis (NpHtrII) in complex with sensory rhodopsin II (NpSRII) were investigated by site-directed spin labeling electron paramagnetic resonance. A series of spin labeled mutants were engineered in NpHtrII157, a truncated analog containing only the first HAMP domain following the transmembrane helix 2. This truncated transducer is shown to be a valid model system for a signal transduction domain anchored to the transmembrane light sensor NpSRII. The HAMP domain is found to be engaged in a "two-state" equilibrium between a highly dynamic (dHAMP) and a more compact (cHAMP) conformation. The structural properties of the cHAMP as proven by mobility, accessibility, and intra-transducer-dimer distance data are in agreement with the four helical bundle NMR model of the HAMP domain from Archaeoglobus fulgidus.
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