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Gene Review

cob  -  cytochrome b

Chlamydomonas reinhardtii

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High impact information on cob

  • The complex has a cytochrome b core and a central quinone exchange cavity, defined by the two monomers that are very similar to those in the respiratory cytochrome bc1 complex [1].
  • A respiratory-deficient strain lacking a 1.2-kb mitochondrial DNA region including the left telomere and part of the cob gene could be rescued as well as a double-frameshift mutant in the mitochondrial cox1 and nd1 genes [2].
  • Myxothiazol-resistant transformants have been created by introducing a nucleotide substitution into the cob gene [2].
  • In comparison to the wild-type strain, all mutants contain an identical point mutation in the cyt b gene, leading to a change of a phenylalanine codon to a leucine codon at amino acid position 129 of the cytochrome b protein [3].
  • Mitochondrial genetics of Chlamydomonas reinhardtii: resistance mutations marking the cytochrome b gene [3].

Biological context of cob

  • Using a set of seven oligonucleotide probes, restriction fragments containing the mitochondrial cytochrome b (cyt b) gene from C. reinhardtii were isolated from a mitochondrial DNA library [3].
  • Based on the nucleotide (nt) sequences of cob and L2a, two oligodeoxyribonucleotides (oligos) were synthesized and used in the polymerase chain reaction (PCR) to amplify the termini of the Chlamydomonas reinhardtii mitochondrial (mt) genome [4].
  • The mitochondrial cob gene from the green alga Chlorogonium elongatum (Chlamydomonadaceae) is interrupted by two group-I introns each containing an open reading frame in-phase with the upstream exon [5].
  • We successively backcrossed (to F(5)) two interfertile strains of the unicellular isogamous haploid algae Chlamydomonas reinhardtii and Chlamydomonas smithii to match nuclear backgrounds and examine transmission patterns of mitochondrial DNA by PCR analysis of cob gene sequences [6].
  • The Polytomella spp. cytochrome b gene is 1113 bp long and does not contain introns [7].

Associations of cob with chemical compounds

  • A comparison of the primary sequences of the Polytomella spp. cytochrome b with other b-type cytochromes, and its analysis based on the structure featuring eight transmembrane stretches, allowed the identification of a tyrosine in position 114, which substitutes for a tryptophan present in all mitochondrial b-type cytochromes sequenced to date [7].
  • In addition, the primary sequence of the cytochrome b from Polytomella spp. has a serine at position 36, instead of a nonpolar residue (alanine or leucine) found in all other species [7].

Other interactions of cob

  • However, the C. reinhardtii petA transformants accumulated lower levels of cytochrome b ( 6 ) /f complexes and exhibited lower light saturated rates of O(2) evolution than C. reinhardtii wild type [8].
  • In mcd1 mutants, which are non-photosynthetic, petD mRNA is degraded by a 5'-3' exonuclease activity, resulting in a failure to synthesize its product, subunit IV of the cytochrome b (6)/f complex [9].


  1. Transmembrane traffic in the cytochrome b6f complex. Cramer, W.A., Zhang, H., Yan, J., Kurisu, G., Smith, J.L. Annu. Rev. Biochem. (2006) [Pubmed]
  2. High-efficiency biolistic transformation of Chlamydomonas mitochondria can be used to insert mutations in complex I genes. Remacle, C., Cardol, P., Coosemans, N., Gaisne, M., Bonnefoy, N. Proc. Natl. Acad. Sci. U.S.A. (2006) [Pubmed]
  3. Mitochondrial genetics of Chlamydomonas reinhardtii: resistance mutations marking the cytochrome b gene. Bennoun, P., Delosme, M., Kück, U. Genetics (1991) [Pubmed]
  4. Amplification and characterization of an inverted repeat from the Chlamydomonas reinhardtii mitochondrial genome. Ma, D.P., King, Y.T., Kim, Y., Luckett, W.S., Boyle, J.A., Chang, Y.F. Gene (1992) [Pubmed]
  5. The apocytochrome-b gene in Chlorogonium elongatum (Chlamydomonadaceae): an intronic GIY-YIG ORF in green algal mitochondria. Kroymann, J., Zetsche, K. Curr. Genet. (1997) [Pubmed]
  6. Strict paternal transmission of mitochondrial DNA of Chlamydomonas species is explained by selection against maternal nucleoids. Nakamura, S., Aoyama, H., van Woesik, R. Protoplasma (2003) [Pubmed]
  7. Two unusual amino acid substitutions in cytochrome b of the colorless alga Polytomella spp.: correlation with the atypical spectral properties of the bH heme. Antaramian, A., Funes, S., Vázquez-acevedo, M., Atteia, A., Coria, R., González-Halphen, D. Arch. Biochem. Biophys. (1998) [Pubmed]
  8. Cytochrome f from the Antarctic psychrophile, Chlamydomonas raudensis UWO 241: structure, sequence, and complementation in the mesophile, Chlamydomonas reinhardtii. Gudynaite-Savitch, L., Gretes, M., Morgan-Kiss, R.M., Savitch, L.V., Simmonds, J., Kohalmi, S.E., Hüner, N.P. Mol. Genet. Genomics (2006) [Pubmed]
  9. A spontaneous tRNA suppressor of a mutation in the Chlamydomonas reinhardtii nuclear MCD1 gene required for stability of the chloroplast petD mRNA. Murakami, S., Kuehnle, K., Stern, D.B. Nucleic Acids Res. (2005) [Pubmed]
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