Molecular mechanisms controlling proton pumping by bacteriorhodopsin. Final report

Crouch, Rosalie K. ; Ebrey, Thomas G.

Medical University of South Carolina, Charleston, S.C. (United States)

关键词: Biochemical Reaction Kinetics;    Amino Acids;    Absorption Spectroscopy;    59 Basic Biological Sciences;    Proteins;   

DOI  :  10.2172/765955
RP-ID  :  none
RP-ID  :  FG02-95ER20171
RP-ID  :  765955

美国|英语

来源: UNT Digital Library

【 摘 要 】

Bacteriorhodopsin (bR) is the simplest biological system for the transduction of light energy. Light energy is directly converted to transmembrane proton gradient by a single, small membrane protein. The extraordinary stability of bR makes it an outstanding subject for bioenergetic studies. This project has focused on the role of interactions between key residues of the pigment involved in light-induced proton transfer. Methods to estimate the strength of these interactions and their correlation with the rate and efficiency of proton transfer have been developed. The concept of the coupling of the protonation states of key groups has been applied to individual steps of the proton transfer with the ultimate goal of understanding on the molecular level the driving forces for proton transport and the pathway of the transported proton in bT. The mechanism of light-induced proton release, uptake and the mechanism of recovery of initial state of bT has been examined. The experiments were performed with genetically engineered, site-specific mutants of bR. This has enabled us to characterize the role of individual amino acid residues in bR. Time resolved and low temperature absorption spectroscopy and light-induced photocurrent measurements were used in order to study the photochemical cycle and proton transfer in mutant pigments. Chemical modification and crosslinking of both the specific amino acids to the chromophore or to other amino acids were used to elucidate the role of light-induced conformational changes in the photocycle and the structure of the protein in the ground state. The results of this project provided new knowledge on the architecture of the proton transfer pathways inside the protein, on the mechanism of proton release in bR, and on the role of specific amino acid residues in the structure and function of bR.