Protein Sequence Homologies between Portions of the L and M Subunits of Reaction Centers of Rhodopseudomonas capsulata and the Qв-Protein of Chloroplast Thylakoid Membranes: a Proposed Relation to Quinone-Binding Sites

Abstract

Sequence homology has been found between the L and M subunits of Rhodopseudomonas capsulata reaction centers and the Qв-protein from all species thus far sequenced. The homology between the L subunit and the Qв-protein is contained in the sequence PFHMLG---F----AMHG-LV-S and is believed to have survived three billion years of evolution. A model is presented which associates quinone binding with this highly conserved sequence.