Cross-species conservation of lipid binding sites on the intramembrane surface of the bacterial reaction centre

Abstract

X-ray crystallography has shown that the Rhodobacter sphaeroides reaction centre engages in a specific interaction with a molecule of the anionic phospholipid cardiolipin (diphosphatidyl glycerol). We have used extensive sequence alignments to determine the degree to which the residues that interact with the cardiolipin are conserved in other species of photosynthetic bacteria with this type of reaction centre. We discuss the possibility that this "cardiolipin binding site" is a conserved feature of these reaction centres. We also discuss the cross-species conservation of residues involved in lipid binding in a recently-reported X-ray crystal structure for the reaction centre from Thermochromatium tepidum, and compare the structure of this reaction centre with the complex from Rhodobacter sphaeroides.