title: Anabaena sensory rhodopsin is a light-driven unidirectional rotor.
abstract: The implementation of multiconfigurational quantum chemistry methods into a quantum-mechanics/molecular-mechanics protocol has allowed the construction of a realistic computer model for the sensory rhodopsin of the cyanobacterium Anabaena PCC 7120. The model, which reproduces the absorption spectra of both the all-trans and 13-cis forms of the protein and their associated K and L intermediates, is employed to investigate the light-driven steps of the photochromic cycle exhibited by the protein. It is found that the photoisomerizations of the all-trans and 13-cis retinal chromophores occur through unidirectional, counterclockwise 180° rotations of the =C14-C15= moiety with respect to the Lys210-linked end of the chromophore axis. Thus, the sequential interconversions of the all-trans and 13-cis forms during a single photochromic cycle yield a complete (360°) unidirectional rotation of the =C14-C15= moiety. This finding implies that Anabaena sensory rhodopsin is a biological realization of a light-driven molecular rotor.
authors.affiliation: Dipartimento di Chimica, Università di Siena, Siena I-53100, Italy.
authors.forename: Angela
authors.initials: A
authors.lastname: Strambi
authors.forename: Bo
authors.initials: B
authors.lastname: Durbeej
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
mesh_terms: D017033:Anabaena / Q000737:chemistry*; D003198:Computer Simulation; D008027:Light; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000378:metabolism*; D015394:Molecular Structure; D011789:Quantum Theory; D025603:Sensory Rhodopsins / Q000737:chemistry* / Q000378:metabolism*; D055672:Static Electricity
chemical_list: D020409:Molecular Motor Proteins; D025603:Sensory Rhodopsins