The Signal Transfer from the Receptor NpSRII to the Transducer NpHtrIl Is Not Hampered by the D75N Mutation

Autor(en): Holterhues, Julia
Bordignon, Enrica
Klose, Daniel 
Rickert, Christian
Klare, Johann P.
Martell, Swetlana
Li, Lin
Engelhard, Martin
Steinhofft, Heinz-Juergen
Stichwörter: Biophysics; COLOR DISCRIMINATION; DOMAIN; HELIX-F; MICROBIAL RHODOPSINS; NATRONOBACTERIUM-PHARAONIS; NATRONOMONAS-PHARAONIS; PHOTOCYCLE; SENSORY-RHODOPSIN-II; TIME-RESOLVED DETECTION; TRANSIENT MOVEMENT
Erscheinungsdatum: 2011
Herausgeber: CELL PRESS
Journal: BIOPHYSICAL JOURNAL
Volumen: 100
Ausgabe: 9
Startseite: 2275
Seitenende: 2282
Zusammenfassung: 
Sensory rhodopsin II (NpSRII) is a phototaxis receptor of Natronomonas pharaonis that performs its function in complex with its cognate transducer (NpHtrII). Upon light activation NpSRII triggers by means of NpHtrII a signal transduction chain homologous to the two component system in eubacterial chemotaxis. The D75N mutant of NpSRII, which lacks the blue-shifted M intermediate and therefore exhibits a significantly faster photocycle compared to the wild-type, mediates normal phototaxis responses demonstrating that deprotonation of the Schiff base is not a prerequisite for transducer activation. Using site-directed spin labeling and time resolved electron paramagnetic-resonance spectroscopy, we show that the mechanism revealed for activation of the wild-type complex, namely an outward tilt motion of the cytoplasmic part of the receptor helix F and a concomitant rotation of the transmembrane transducer helix TM2, is also valid for the D75N variant. Apparently, the D75N mutation shifts the ground state conformation of NpSRII-D75N and its cognate transducer into the direction of the signaling state.
ISSN: 00063495
DOI: 10.1016/j.bpj.2011.03.017

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