title: Photoproducts of bacteriorhodopsin mutants: a molecular dynamics study.
abstract: Molecular dynamics simulations of wild-type bacteriorhodopsin (bR) and of its D85N, D85T, D212N, and Y57F mutants have been carried out to investigate possible differences in the photoproducts of these proteins. For each mutant, a series of 50 molecular dynamics simulations of the photoisomerization and subsequent relaxation process were completed. The photoproducts can be classified into four distinct classes: 1) 13-cis retinal, with the retinal N-H+ bond oriented toward Asp-96; 2) 13-cis retinal, with the N-H+ oriented toward Asp-85 and hydrogen-bonded to a water molecule; 3) 13,14-di-cis retinal; 4) all-trans retinal. Simulations of wild-type bR and of its Y57F mutant resulted mainly in class 1 and class 2 products; simulations of D85N, D85T, and D212N mutants resulted almost entirely in class 1 products. The results support the suggestion that only class 2 products initiate a functional pump cycle. The formation of class 1 products for the D85N, D85T, and D212N mutants can explain the reversal of proton pumping under illumination by blue and yellow light.
authors.affiliation: Beckman Institute, University of Illinois at Urbana-Champaign 61801, USA.
authors.forename: W
authors.initials: W
authors.lastname: Humphrey
authors.forename: E
authors.initials: E
authors.lastname: Bamberg
authors.forename: K
authors.initials: K
authors.lastname: Schulten
mesh_terms: D000595:Amino Acid Sequence; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000528:radiation effects; D001665:Binding Sites; D003198:Computer Simulation; D006860:Hydrogen Bonding; D007536:Isomerism; D008958:Models, Molecular; D008961:Models, Structural; D010782:Photolysis; D017354:Point Mutation; D012172:Retinaldehyde / Q000378:metabolism; D012545:Schiff Bases; D012984:Software; D013816:Thermodynamics; D014867:Water
chemical_list: D012545:Schiff Bases; D014867:Water; D001436:Bacteriorhodopsins; D012172:Retinaldehyde