Structure of the photosynthetic reaction centre from Rhodobacter sphaeroides at 2.65 å resolution: cofactors and protein-cofactor interactions

Abstract

The cofactor arrangement and the mode of binding to the protein seem to be very similar among the non-sulphur bacterial photosynthetic RCs. The functional role of the displaced QB molecule, which might be present as quinol, rather than quinone, is not yet clear. The newly discovered water chain to the QB binding site suggests a pathway for the protonation of the secondary quinone QB.

Trapped Conformational States of Semiquinone (D+•QB-•) Formed by B-Branch Electron Transfer at Low Temperature in Rhodobacter sphaeroides Reaction Centers

“…Since binding to these two sites is nearly isoenergetic, small changes in the binding free energy resulting from temperature or external solvent could lead to a change in the relatively occupancy. This may be one reason for the reported differences in the binding position of Q B (26)(27)(28)(29)(30)69) and the FTIR observation that Q B prefers to bind at the proximal position at room temperature (46). …”

The Open, the Closed, and the Empty: Time-Resolved Fluorescence Spectroscopy and Computational Analysis of RC-LH1 Complexes from Rhodopseudomonas palustris

“…14,15 Each subunit accommodates two light harvesting BChl a molecules giving rise to an absorption band at 875 nm. The reaction center complex accommodates a BChl a dimer (special pair, primary donor, P), two accessory BChl a molecules (B A , B B ), two bacteriopheophytin a (BPheo a) molecules (H A , H B ), and two ubiquinones (Q A , Q B ) bound to two protein subunits denoted L and M. The cofactors are arranged in two nearly identical branches, called A and B, which share the primary donor, P. 9,11,16,17 In particular the RC from Rhodobacter (Rb.) sphaeroides has served as a cornerstone for elucidating structure−function relationships employing a large variety of spin resonance 18−23 and optical spectroscopies.…”

Crystallization and X‐ray analysis of the reaction center from the thermophilic green bacterium Chloroflexus aurantiacus

“…viridis and Rb. sphaeroides have been crystallized and their structures elucidated at atomic resolution [2][3][4][5][6]. Most RCs are comprised of three protein subunits which are called H (heavy), M (medium) and L (light) according to their electrophoretic mobilities in SDS-PAGE.…”

“…viridis was the first membrane protein to be crystallized and its threedimensional structure to be solved at atomic resolution [2,13,14]. Subsequently, the structure of three-dimensional crystals of a few other membrane proteins have been determined [2,[4][5][6][15][16][17][18][19]. Despite these achievements, it is still a challenge to obtain crystals of integral membrane proteins which are suitable for subsequent structure analysis.…”