Evolutionary conservation of protein regions in the protonmotive cytochromeb and their possible roles in redox catalysis
- 149 Downloads
The amino acid sequences of the protonmotive cytochromeb from seven representative and phylogenetically diverse species have been compared to identify protein regions or segments that are conserved during evolution. The sequences analyzed included both prokaryotic and eukaryotic examples as well as mitochondrial cytochromeb and chloroplastb6 proteins. The principal conclusion from these analyses is that there are five protein regions-each comprising about 20 amino acid residues—that are consistently conserved during evolution. These domains are evident despite the low density of invariant residues. The two most highly conserved regions, spanning approximately consensus residues 130–150 and 270–290, are located in extramembrane loops and are hypothesized to constitute part of the Qo reaction center. The intramembrane, hydrophobic protein regions containing the heme-ligating histidines are also conserved during evolution. It was found, however, that the conservation of the protein segments extramembrane to the histidine residues ligating the low potential b566 heme group showed a higher degree of sequence conservation. The location of these conserved regions suggests that these extramembrane segments are also involved in forming the Qo reaction center. A protein segment putatively constituting a portion of the Qi reaction center, located approximately in the region spanned by consensus residues 20–40, is conserved in species as divergent as mouse andRhodobacter. This region of the protein shows substantially less sequence conservation in the chloroplast cytochromeb6. The catalytic role of these conserved regions is strongly supported by locations of residues that are altered in mutants resistant to inhibitors of cytochromeb electron transport.
Key wordsCytochromeb Electron transport Protein evolution Membrane proteins Mitochondria Chloroplasts Protein domains
Unable to display preview. Download preview PDF.
- Berry EA, Trumpower BL (1985) Pathways of electrons and protons through the cytochromebc1 complex of the mitochondrial respiratory chain. In: Lenaz G (ed) Coenzyme Q. Biochemistry, bioenergetics and clinical applications of ubiquinone. John Wiley & Sons, New York, pp 365–389Google Scholar
- Cramer WA, Black MT, Widger WR, Girvin ME (1987) Structure and function of photosynthetic cytochromeb/c 1 andb 6-f complexes. In: Barber J (ed) The light reactions. Elsevier, Amsterdam, pp 447–493Google Scholar
- Crofts A, Robinson H, Andrews K, Van Doren S, Berry E (1987) Catalytic sites for reduction and oxidation of quinones. In: Papa S, Chance B, Ernster L (eds) Cytochrome systems. Molecular biology and bioenergetics. Plenum, New York, pp 617–624Google Scholar
- Dawson AJ, Jones VP, Leaver CJ (1984) The apocytochromeb gene in maize mitochondria does not contain introns and is preceded by a potential ribosome binding site. EMBOJ 3:2107–2113Google Scholar
- de la Cruz V, Neckelmann N, Simpson L (1984) Sequences of six genes and several open reading frames in the kinetoplast maxicircle DNA ofLeishmania tarentolae. J Biol Chem 259:15135–15147Google Scholar
- Feng DF, Johnson MS, Doolittle RF (1985) Aligning amino acid sequences: comparison of commonly used methods. J Mol Evol 21:112–125Google Scholar
- French S, Robson B (1983) What is a conservative substitution? J Mol Evol 19:171–175Google Scholar
- Howell N, Gilbert K (1987) Sequence analysis of mammalian cytochromeb mutants. In: Papa S, Chance B, Ernster L (eds) Cytochrome systems: molecular biology and bioenergetics. Plenum, New York, pp 79–86Google Scholar
- Mitchell P (1987) Respiratory chain systems in theory and practice. In: Kim CH, Tedeschi H, Diwan JJ, Salerno JC (eds) Advances in membrane biochemistry and bioenegetics. Plenum, New York, pp 25–52Google Scholar
- Schwartz RM, Dayhoff MO (1978) Matrices for detecting distant relationships. In: Dayhoff M (ed) Atlas of protein sequence and structure, vol 5, suppl 3. National Biomedical Research Foundation, Silver Springs MD, pp 353–358Google Scholar