THE NUCLEOTIDE-SEQUENCE OF THE PUF OPERON FROM THE PURPLE PHOTOSYNTHETIC BACTERIUM, RHODOSPIRILLUM-MOLISCHIANUM - COMPARATIVE ANALYSES OF LIGHT-HARVESTING PROTEINS AND THE CYTOCHROME SUBUNITS ASSOCIATED WITH THE REACTION CENTERS

The nucleotide sequence of the puf operon of the purple bacterium, Rho dospirillum molischianum, was determined. The operon includes genes co ding for the beta and alpha subunits of the light-harvesting 1 (LH1) c omplex and the L, M, and cytochrome subunits of the reaction center co mplex. As in other purple bacteria, the genes are arranged within the operon in this order. As in Rubrivivax gelatinosus, the deduced amino acid sequence of the cytochrome subunit in Rsp. molischianum contains significant deletions at the attachment site to the M subunit compared with that of Rhodopseudomonas viridis. This suggests that the interac tion between the cytochrome subunit and the LM core in Rsp. molischinu m and Rvi. gelatinosus is different from that in Rps. viridis. Phyloge netic analysis of the light-harvesting proteins indicated that the LH1 alpha and beta subunits of Rsp. molischianum are included in the line age of LH1 polypeptides of the purple bacteria, while the LH2 alpha an d beta subunits are positioned apart from LH2 polypeptides of the othe r purple bacteria together with those of Chromatium vinosum. Based on these phylogenetic analyses, the classification of the light-harvestin g proteins in purple bacteria is discussed.