Probing the Bacteriochlorophyll Binding Site Requirements of the Core Light-Harvesting Complex of Photosynthetic Bacteria Using BChl Analogs

Abstract

The methodology developed (1–3) for reconstitution of the light-harvesting (LH) complex of Rhodospirillum rubrum, B873, and its structural subunit (B820) has made it possible to begin probing structural requirements of the bacteriochlorophyll (BChl) binding site(s). Using the separately-isolated α- and β-polypeptides of R. rubrum and a series of BChl a analogs, evidence was obtained for the importance of three functional groups and of the oxidation state of the macrocyclic ring for B820 and B873 formation, as well as for a role for the esterifying alcohol (tail) in stabilizing the B820 complex. In this paper, the results are summarized and the role of the esterifying alcohol in B820 and B873 formation is discussed. A more detailed account of the experiments and methodology will be published elsewhere.