High impact information on COB

• The region coding for apocytochrome b in the mitochondrial genome of Saccharomyces cerevisiae is believed to exhibit a mosaic organization, consisting in certain strains of five exons and four introns [1].
• Assembly of the mitochondrial membrane system. Processing of the apocytochrome b precursor RNAs in Saccharomyces cerevisiae D273-10B [2].
• The second series of mutations, generating new polypeptides ranging in size from 17,000 to 41,000 daltons, is located within the first intervening sequence (alpha/beta) of the split gene for apocytochrome b [3].
• Revertants fall into three classes: on galactose two produce a polypeptide indistinguishable from apocytochrome b, but vary in its amount, while the third fails to increase apocytochrome b above mutant levels [4].
• The wheat mitochondrial gene for apocytochrome b (CYB) has been identified by its hybridization to a yeast CYB probe and its nucleotide sequence has been determined [5].

Biological context of COB

• In contrast, mutations in putative intervening sequences often led to multiple new polypeptides immunologically related to apocytochrome b [6].
• The wheat mitochondrial gene for apocytochrome b: absence of a prokaryotic ribosome binding site [5].
• First analysis of transcripts by electrophoresis and RNA/DNA-hybridization clearly showed that cell growth in the presence of CAP leads to an inhibition of processing yielding an increasing amount of splicing intermediates of the COB transcript and decreasing amounts of the 18S mRNA coding for apocytochrome b [7].
• The apocytochrome b gene, exclusively encoded by the mitochondrial genome, was engineered so that it could be expressed in the yeast cytoplasm [8].
• Sequence analysis of the mutations, which previously were shown to cause premature termination of apocytochrome b, revealed that two of them directly transform sense codons to chain-termination codons, whereas the other four are frame-shift mutations (+1/-1, insertions/deletions) [9].

Anatomical context of COB

• Limitations to in vivo import of hydrophobic proteins into yeast mitochondria. The case of a cytoplasmically synthesized apocytochrome b [8].

Associations of COB with chemical compounds

• A nonsense mutation of the leucine codon 335 (TTA-->TAA), 50 residues before the normal C-terminus, blocks incorporation of heme into the apocytochrome b and prevents growth on non-fermentable substrates [10].

Analytical, diagnostic and therapeutic context of COB

• We show that this translation product is identical with apocytochrome b using peptide mapping by limited proteolysis according to Cleveland et al [11].

References