Demonstration of a sensory rhodopsin in eubacteria.

摘要: We report the first sensory rhodopsin observed in eubacterial domain, a green light-activated photoreceptor Anabaena (Nostoc) sp. PCC7120, freshwater cyanobacterium. The gene encoding membrane opsin protein of 261 residues (26 kDa) and smaller soluble 125 (14 are under same promoter single operon. expressed heterologously Escherichia coli membranes bound all-trans retinal to form pink pigment (lambda max 543 nm) with photochemical reaction cycle 110 ms half-life (pH 6.8, 18 degrees C). Co-expression 14 kDa increased rate photocycle, indicating physical interaction membrane-embedded rhodopsin, which we confirmed vitro by affinity enrichment chromatography Biacore interaction. lacks proton donor carboxylate residue helix C conserved known retinylidene pumps did not exhibit detectable ejection activity. detected binding SDS-PAGE autofluorography 3H-labelled reduced from organism. conclude that functions as photosensory receptor its natural environment, suggest transduces signal receptor. Therefore, unlike archaeal rhodopsins, transmit signals transmembrane helix-helix interactions transducers, may through cytoplasmic protein, analogous higher animal visual pigments.