Characterization of a cDNA encoding subunit VI of cytochrome c oxidase from the slime mold Dictyostelium discoideum

Purification and characterization of cytochrome c oxidase from the insect trypanosomatid Crithidia fasciculata

Cytochrome c oxidase was purified from the mitochondrial lysate of the insect trypanosomatid Crithidia fasciculata with the aid of a methyl hydrophobic interaction column in a rapid one-step procedure. The purified complex displayed all characteristics expected from a eukaryotic cytochrome c oxidase: the presence of CuA in electron paramagnetic resonance analysis, a characteristic 605 nm peak in reduced-minus-oxidized optical spectroscopy, and the capacity to efficiently oxidize homologous, but not heterologous, cytochrome c. Two-dimensional PAGE showed that C. fasciculata cytochrome c oxidase consists of at least 10 different subunits. N-terminal sequences were obtained from the six smallest subunits of the complex, one of them showing significant similarity to Neurospora crassa cytochrome c oxidase subunit V. The N-terminus of each of the four largest subunits was found to be blocked.

The sequence of a small subunit of cytochrome c oxidase from Crithidia fasciculata which is homologous to mammalian subunit IV

The sequence of subunit 8 of cytochrome c oxidase from Crithidia fasciculata was determined by sequencing cDNA and N-terminus of the mature protein (Mr = 15.7 kDA). The (inferred) protein is homologous to mammalian cox IV and the corresponding cox subunits from yeast, Neurospora crassa and Dictyostelium discoideum, which is reflected in a very similar hydropathy profile. Elements that are conserved in the C. fasciculata sequence include (i) an N-terminal (D/E)-(K/R)-X-K-(X2)-W-(X2)-(I/L) motif, (ii) a putative membrane-spanning region in the middle portion of the protein, and (iii) a C-terminal W-(X13)-(N/D)-P motif. The C. fasciculata protein is synthesized with a cleavable presequence.

The most conserved nuclear-encoded polypeptide of cytochrome c oxidase is the putative zinc-binding subunit: primary structure of subunit V from the slime mold Dictyostelium discoideum

A full-length 515 base pairs cDNA for cytochrome c oxidase subunit V of D. discoideum was isolated from a lambda gt11 expression library. The encoded polypeptide, whose identity was confirmed by partial protein sequencing, is 119 amino acids long (Mr = 13,352) and does not contain a cleavable presequence. The protein, which is homologous to human subunit Vb and yeast subunit IV, exhibits the highest degree of sequence conservation found among nuclear-encoded subunits of cytochrome c oxidase from distantly related organisms. All the invariant residues are clustered in two regions of the C-terminus which include the putative amino acids involved in the coordination of the Zn ion tightly associated to eukaryotic oxidase.