Primary structure of the L subunit of the reaction center from Rhodopseudomonas sphaeroides
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.
Additional Information© 1984 by the National Academy of Sciences. Contributed by G. Feher, August 1, 1984. We thank E. Abresch for the preparation of the RCs, L.-P. Li for assistance in peptide preparation and analysis, R.F. Doolittle for the computer alignments of homologous protein sequences, and R. Theiler and D.C. Youvan for access to unpublished material. This work was supported by grants from the National Institutes of Health (GM 07313 and 13191), the National Science Foundation (PCM 82-02811), and the Office of Naval Research (N00014-83-K-0079). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Published - WILpnas84.pdf