Amino acid sequences of two high-potential iron-sulfur proteins (HiPIPs) from the moderately halophilic purple phototrophic bacterium, Rhodospirillumsalinarum
Rp. Ambler et al., Amino acid sequences of two high-potential iron-sulfur proteins (HiPIPs) from the moderately halophilic purple phototrophic bacterium, Rhodospirillumsalinarum, ARCH BIOCH, 369(1), 1999, pp. 143-148
The amino acid sequences of two very different high-potential iron-sulfur p
rotein (HiPIP) isozymes have been determined from the moderately halophilic
purple phototrophic bacterium, Rhodospirillum salinarum. Iso-1 HiPIP, whic
h is monomeric and contains 57 amino acid residues, is most similar to the
Thiobacillus ferrooxidans iron-oxidizing enzyme (45% identity and a 6-resid
ue deletion). On the other hand, iso-2 HiPIP, which is isolated as an oligo
mer, contains a peptide chain with 54 amino acid residues. It is the smalle
st reported to date and is only 31% identical to iso-1 HiPIP. A massive del
etion 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 inser
tion and a 5-residue deletion. Prior to this study, there were only 2 absol
utely conserved residues (Tyr 19 and Gly 75, Chromatium numbering) in addit
ion to the 4 iron-sulfur cluster binding cysteine residues among the 13 HiP
IPs sequenced to date. We found that Tyr 19 is absent in iso-2 HiPIP along
with the entire N-terminal loop. Moreover, Gay 75 is substituted in both R.
salinarum HiPIPs. These characteristics make the R. salinarum HiPIPs, and
especially iso-2, the most divergent yet characterized. (C) 1999 Academic P
ress