Complementary DNA encoding core protein II of human mitochondrial cytochrome bc1 complex. Substantial diversity in deduced primary structure from its yeast counterpart.
Core protein II of mitochondrial cytochrome bc1 complex is the second largest nuclear-encoded subunit that is essential for the assembly of the functional complex. We have isolated, for the first time, a cDNA clone for a mammalian core protein II. Immunoscreening of a lambda gt11 rat liver cDNA library resulted in isolation of a cDNA encoding a partial sequence of rat mitochondrial core protein II, and this cloned cDNA was used as a probe for colony hybridization to screen a human fibroblast cDNA library. By comparison with the known NH2-terminal amino acid sequence of bovine core protein II, the amino acid sequence deduced from a cloned human cDNA was predicted to be composed of the part for the NH2-terminal extension of 14 amino acid residues and that for the mature polypeptide of 439 residues. The presequence is typical of precursors to mitochondrial proteins in being composed of a combination neutral and basic residues. The deduced sequence shows rather low homology with that of the corresponding subunit of yeast cytochrome bc1 complex; this finding is in contrast with the relatively high homology observed for the sequences of the redox center-carrying subunits of the same complex. On Northern blot analysis of human fibroblast poly(A)+ RNA, the cDNA hybridized to two mRNAs, a major species of 1700 nucleotides and a minor one of 2000 nucleotides. Southern blot hybridization of genomic DNA suggested that the human genome contains one or two genes for core protein II.
Hosokawa
Y
Y
Department of Biomedical Chemistry, Faculty of Medicine, University of Nagoya, Japan.
Suzuki
H
H
Toda
H
H
Nishikimi
M
M
Ozawa
T
T
D000595:Amino Acid Sequence; D001483:Base Sequence; D004247:DNA / Q000235:genetics*; D014450:Electron Transport Complex III / Q000235:genetics*; D005796:Genes; D006801:Humans; D046911:Macromolecular Substances; D008930:Mitochondria, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D046911:Macromolecular Substances; D004247:DNA; D014450:Electron Transport Complex III