Characterization of two cytochrome b 6 proteins from the cyanobacterium Gloeobacter violaceus PCC 7421
In the genome of the untypical cyanobacterium Gloeobacter violaceus PCC 7421 two potential cytochrome b 6 proteins PetB1 and PetB2 are encoded. Such a situation has not been observed in cyanobacteria, algae and higher plants before, and both proteins are not characterized at all yet. Here, we show that both apo-proteins bind heme with high affinity and the spectroscopic characteristics of both holo-proteins are distinctive for cytochrome b 6 proteins. However, while in PetB2 one histidine residue, which corresponds to H100 and serves as an axial ligand for heme b H in PetB1, is mutated, both PetB proteins bind two heme molecules with different midpoint potentials. To recreate the canonical heme b H binding cavity in PetB2 we introduced a histidine residue at the position corresponding to H100 in PetB1 and subsequently characterized the generated protein variant. The presented data indicate that two bona fide cytochrome b 6 proteins are encoded in Gloeobacter violaceus. Furthermore, the two petB genes of Gloeobacter violaceus are each organized in an operon together with a petD gene. Potential causes and consequences of the petB and petD gene heterogeneity are discussed.
KeywordsAssembly Cyanobacteria Cytochrome b6 Heme Cofactor
Unable to display preview. Download preview PDF.
- Kallas T (1994) In the molecular biology of cyanobacteria: the cytochrome b6f complex. In: Bryant DA (ed). Kluwer Academic Publishers, Dordrecht, pp 259–317Google Scholar
- Kallas T, Spiller S, Malkin R (1988) J Biol Chem 263:14334–14342Google Scholar
- Ozols J, Strittmatter P (1964) J Biol Chem 239:1018–1023Google Scholar
- Schmetterer G (1994) In: Bryant DA (ed) The molecular biology of cyanobacteria: cyanobacterial respiration. Kluwer, Dordrecht, pp 409–435Google Scholar
- Schneider D, Schmidt CL (2005) Biochim Biophys Acta 1710:1–12Google Scholar
- Zito F, Finazzi G, Delosme R, Nitschke W, Picot D, Wollman F-A (1999) EMBO J 18:2961–2969Google Scholar