Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The bax-type cytochrome c oxidase from Thermus thermophilus is known as a two subunit enzyme. Deduced from the crystal structure of this enzyme, we discovered the presence of an additional transmembrane helix "subunit IIa" spanning the membrane. The hydrophobic N-terminally blocked protein was isolated in high yield using high-performance liquid chromatography. Its complete amino acid sequence was determined by a combination of automated Edman degradation of both the deformylated and the cyanogen bromide cleaved protein and automated C-terminal sequencing of the native protein. The molecular mass of 3,794 Da as determined by MALDI-MS and by ESI requires the N-terminal methionine to be formylated and is in good agreement with the value calculated from the formylmethionine containing sequence (3,766.5 Da + 28 Da = 3,794.5 Da). This subunit consits of 34 residues forming one helix across the membrane (Lys5-Ala34), which corresponds in space to the first transmembrane helix of subunit II of the cytochrome c oxidases from Paracoccus denitrificans and bovine heart, however, with opposite polarity. It is 35% identical to subunit IV of the ba3-cytochrome oxidase from Natronobacterium pharaonis. The open reading frame encoding this new subunit IIa (cbaD) is located upstream of cbaB in the same operon as the genes for subunit I (cbaA) and subunit II (cbaB).
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PMID:Primary structure of a novel subunit in ba3-cytochrome oxidase from Thermus thermophilus. 1115 18

Cox17, a copper chaperone for cytochrome-c oxidase, contains six conserved Cys residues and exists in three oxidative states, linked with two thiol-based redox switches. The first switch leads to formation of two disulfides and occurs upon transport of Cox17 into mitochondrial intermembrane space (IMS). Cox17(2S-S) is retained in the IMS and is also a functional form of the protein, which can be further oxidized to Cox17(3S-S). According to the midpoint redox potential values, Cox17 can be partially oxidized in the cytosol, which might hinder its transport into IMS. We hypothesize that Zn(II) ions might protect cytosolic Cox17 from oxidation. In order to get quantitative information about the modulatory effect of Zn(II) ions on redox switches in Cox17, we have used ESI MS for determination of the midpoint potentials for redox couples of Cox17: Cox17(3S-S) <--> Cox17(2S-S) (E(m1)) and Cox17(2S-S) <--> Cox17(0S-S) (E(m2)) in the presence of Zn(II). 10 microM Zn(II) ions shift the E(m2) by 21 mV and E(m1) by 15 mV to more positive values. Apparent dissociation constants for Zn(II) complexes of Cox17(0S-S) and Cox17(2S-S), are 0.067 and 0.29 nM, respectively. The high affinity shows that metallation of Cox17(0S-S) by Zn(II) might be significant in cellular conditions, which might protect Cox17 from oxidation and enable its transport into IMS.
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PMID:Modulation of redox switches of copper chaperone Cox17 by Zn(II) ions determined by new ESI MS-based approach. 1901 66