2iia
From Proteopedia
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Anabaena sensory rhodopsin transducer
Overview
We present crystal structures of the Anabaena sensory rhodopsin transducer (ASRT), a soluble cytoplasmic protein that interacts with the first structurally characterized eubacterial retinylidene photoreceptor Anabaena sensory rhodopsin (ASR). Four crystal structures of ASRT from three different spacegroups were obtained, in all of which ASRT is present as a planar (C4) tetramer, consistent with our characterization of ASRT as a tetramer in solution. The ASRT tetramer is tightly packed, with large interfaces where the well-structured beta-sandwich portion of the monomers provides the bulk of the tetramer-forming interactions, and forms a flat, stable surface on one side of the tetramer (the beta-face). Only one of our four different ASRT crystals reveals a C-terminal alpha-helix in the otherwise all-beta protein, together with a large loop from each monomer on the opposite face of the tetramer (the alpha-face), which is flexible and largely disordered in the other three crystal forms. Gel-filtration chromatography demonstrated that ASRT forms stable tetramers in solution and isothermal microcalorimetry showed that the ASRT tetramer binds to ASR with a stoichiometry of one ASRT tetramer per one ASR photoreceptor with a K(d) of 8 microM in the highest affinity measurements. Possible mechanisms for the interaction of this transducer tetramer with the ASR photoreceptor via its flexible alpha-face to mediate transduction of the light signal are discussed.
About this Structure
2IIA is a Single protein structure of sequence from Anabaena sp.. Full crystallographic information is available from OCA.
Reference
Crystal structure of the Anabaena sensory rhodopsin transducer., Vogeley L, Trivedi VD, Sineshchekov OA, Spudich EN, Spudich JL, Luecke H, J Mol Biol. 2007 Mar 30;367(3):741-51. Epub 2006 Dec 1. PMID:17289074
Page seeded by OCA on Thu Mar 20 17:29:57 2008
