The primary structure of the Chloroflexus aurantiacus reaction-center polypeptides

The complete nucleotide sequence of two Chloroflexus aurantiacus reaction-center genes has been obtained. The amino acid sequence deduced from the first gene showed 40% similarity to the L subunit of the Rhodobacter sphaeroides reaction center. This L subunit was 310 amino acids long and had an approximate molecular mass of 35 kDa. The second gene began 17 bases downstream from the first gene. The amino acid sequence deduced from it (307 amino acids; 34950 Da) was 42% similar to the M subunit of the Rhodobacter sphaeroides reaction center. 20% of the deduced primary structure were confirmed through automated Edman degradation of cyanogen bromide peptide fragments or N-chlorosuccinimide peptide fragments isolated from the purified reaction-center complex or from the individual subunits. The peptides were isolated by preparative gel electrophoresis combined with molecular sieve chromatography in the presence of a mixture of formic acid, acetonitrile, 2-propanol and water. This method appeared to be applicable to the isolation of other hydrophobic proteins and their peptides.