Abstract
In a recent publication, the structural details of an interaction between the Rhodobacter sphaeroides reaction center and the anionic phospholipid diphosphatidyl glycerol (cardiolipin) were described (K. E. McAuley, P. K. Fyfe, J. P. Ridge, N. W. Isaacs, R. J. Cogdell, and M. R. Jones, 1999, Proc. Natl. Acad. Sci. U.S.A. 96:14706-14711). This was the first crystallographic description of an interaction between this biologically important lipid and an integral membrane protein and was also the first piece of evidence that the reaction center has a specific interaction with cardiolipin. We have examined the extent to which the residues that interact with the cardiolipin are conserved in other species of photosynthetic bacteria with this type of reaction center and discuss the possibility that this cardiolipin binding site is a conserved feature of these reaction centers. We look at how sequence variations that would affect the shape of the cardiolipin binding site might affect the protein-cardiolipin interaction, by modeling the binding of cardiolipin to the reaction center from Rhodopseudomonas viridis.