title: Primary structure of the L subunit of the reaction center from Rhodopseudomonas sphaeroides.
abstract: The reaction center is an integral membrane protein that, together with several cofactors, mediates the primary photochemical events in bacterial photosynthesis. The amino-terminal sequences of the three subunits, L, M, and H, of the reaction center protein and the sequence of the structural gene encoding the M subunit have been reported previously. In the present study, we found that the 3' end of the structural gene encoding the L subunit overlaps by eight bases the 5' end of the gene encoding the M subunit. The primary structure of the L subunit has been determined from the nucleotide sequence of the gene and from analyses of the amino and carboxyl termini of the protein. The sequences of a number of tryptic and chymotryptic peptides were used to corroborate the nucleotide sequence. The L subunit was found to be composed of 281 amino acids (Mr 31,319) and to contain five hydrophobic segments. It is homologous to the M subunit and to a plant thylakoid protein referred to as the QB or Mr 32,000 protein.
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D002918:Chymotrypsin; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D005796:Genes; D005798:Genes, Bacterial; D046911:Macromolecular Substances; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis; D045322:Photosynthetic Reaction Center Complex Proteins; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013045:Species Specificity; D014357:Trypsin
chemical_list: D001426:Bacterial Proteins; D046911:Macromolecular Substances; D010446:Peptide Fragments; D045322:Photosynthetic Reaction Center Complex Proteins; D004262:DNA Restriction Enzymes; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D002918:Chymotrypsin; D014357:Trypsin