title: Amino acid sequences of two high-potential iron-sulfur proteins (HiPIPs) from the moderately halophilic purple phototrophic bacterium, Rhodospirillum salinarum.
abstract: The amino acid sequences of two very different high-potential iron-sulfur protein (HiPIP) isozymes have been determined from the moderately halophilic purple phototrophic bacterium, Rhodospirillum salinarum. Iso-1 HiPIP, which is monomeric and contains 57 amino acid residues, is most similar to the Thiobacillus ferrooxidans iron-oxidizing enzyme (45% identity and a 6-residue deletion). On the other hand, iso-2 HiPIP, which is isolated as an oligomer, contains a peptide chain with 54 amino acid residues. It is the smallest reported to date and is only 31% identical to iso-1 HiPIP. A massive deletion of 17 residues is found at the N-terminus, such that only 2 residues remain prior to the first cysteine. Iso-2 HiPIP also has a 12-residue insertion and a 5-residue deletion. Prior to this study, there were only 2 absolutely conserved residues (Tyr 19 and Gly 75, Chromatium numbering) in addition to the 4 iron-sulfur cluster binding cysteine residues among the 13 HiPIPs sequenced to date. We found that Tyr 19 is absent in iso-2 HiPIP along with the entire N-terminal loop. Moreover, Gly 75 is substituted in both R. salinarum HiPIPs. These characteristics make the R. salinarum HiPIPs, and especially iso-2, the most divergent yet characterized.
authors.affiliation: Institute of Cell and Molecular Biology, University of Edinburgh, Edinburgh, EH9 3JR, Scotland. R.Ambler@ed.ac.uk
authors.forename: R P
authors.initials: RP
authors.lastname: Ambler
authors.forename: M
authors.initials: M
authors.lastname: Daniel
authors.forename: T E
authors.initials: TE
authors.lastname: Meyer
authors.forename: M A
authors.initials: MA
authors.lastname: Cusanovich
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification; D010450:Endopeptidases; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D045322:Photosynthetic Reaction Center Complex Proteins; D010802:Phylogeny; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification; D012246:Rhodospirillum / Q000145:classification / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D010446:Peptide Fragments; D045322:Photosynthetic Reaction Center Complex Proteins; D020033:Protein Isoforms; C007943:high potential iron-sulfur protein; D010450:Endopeptidases