Structural insights into the early steps of receptor-transducer signal transfer in archaeal phototaxis |
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Authors: | Wegener A A Klare J P Engelhard M Steinhoff H J |
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Institution: | Max-Planck-Institut für Molekulare Physiologie, Otto Hahn-Strasse 11, D-44227 Dortmund, Germany. |
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Abstract: | Electron paramagnetic resonance-based inter-residue distance measurements between site-directed spin-labelled sites of sensory rhodopsin II (NpSRII) and its transducer NpHtrII from Natronobacterium pharaonis revealed a 2:2 complex with 2-fold symmetry. The core of the complex is formed by the four transmembrane helices of a transducer dimer. Upon light excitation, the previously reported flap-like movement of helix F of NpSRII induces a conformational change in the transmembrane domain of the transducer. The inter-residue distance changes determined provide strong evidence for a rotary motion of the second transmembrane helix of the transducer. This helix rotation becomes uncoupled from changes in the receptor during the last step of the photocycle. |
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