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R A Capaldi

Publications and source records attributed to R A Capaldi.

At least 181 records · Page 10Linked to original sources
PubMed1977

Nearest neighbor relationships of the polypeptides in ubiquinone cytochrome c reductase (complex III).

Ubiquinone cytochrome c reductase (complex III) in detergent dispersion has been cross-linked with two reversible cross-linking agents dithiobissuccinimidylpropionate and dimethyl-3.3'-dithiobispropionimidate and the cross-linked products formed have been analyzed by two-dimensional gel electrophoresis. Under mild reaction conditions, polypeptides I and II, II and VI, I and V, and VI and VII were the most prominent subunit pairs seen. With higher levels of reagent, larger aggregates were produced until an aggregate of apparent molecular weight 310 000 was the dominant band on gels. This is the complex III monomer.

Cytochrome Reductases↗
PubMed1977

Interaction of detergents with cytochrome c oxidase.

The binding of ionic and nonionic, nondenaturing detergents to cytochrome c oxidase has been examined. All bind and displace part but not all of the phospholipid that is associated with the enzyme after isolation. From 6 to 10 phospholipid molecules, depending on the detergent used, do not exchange and these are mostly diphosphatidylglycerol molecules as first shown by Awasthi et al. ((1971) Biochim. Biophys. Acta 226, 42). The binding of Triton X-100 and deoxycholate to the cytochrome c oxidase complex has been studied in detail. Both bind to the enzyme above their critical micelle concentrations: Triton X-100 in the amount of 180 +/- 10 molecules per complex and deoxycholate in the amount of 80 +/- 4 molecules per complex. In nonionic detergents, cytochrome c oxidase exists as a dimer (4 heme complex). The enzyme is dissociated into the monomer or heme aa3 complex by delipidation in bile salts. Activity measurements in different detergents suggest that cytochrome c oxidase requires a flexible, hydrophobic environment for maximal activity and that the dimer or 4 heme complex may be the active species.

Animals↗
PubMed1977

Near-neighbor relationships of the subunits of cytochrome c oxidase.

Cytochrome c oxidase in detergent dispersion has been cross-linked with two reversible cross-linking agents, dithiobissuccinimidylpropionate (DSP) and dimethyl-3,3'-dithiobispropionimidate (DTBP), and the cross-linked products formed have been analyzed by two-dimensional gel electrophoresis. Under mild reaction conditions, several subunit pairs were seen including II and V, V and VII, IV and VI. With higher levels of DSP, larger aggregates were seen until a cross-linked product with an apparent molecular weight of 140 000 was the predominant band on gels. This is the smallest molecular weight aggregate to contain all seven subunits of the enzyme and most likely represents the "unit" or two heme and two copper containing complex of cytochrome c oxidase.

Animals↗
PubMed1976

The polypeptide composition of ubiquinone-cytochrome c reductase (complex III) from beef heart mitochondria.

The subunit structure of ubiquinone-cytochrome c reductase (complex III) has been examined and eight different polypeptides have been identified. Apparent molecular weights for each have been obtained by one or more methods including polyacrylamide gel electrophoresis in sodium doecyl sulfate and in sodium dodecyl sulfate-8 M urea and by gel filtration in sodium dodecyl sulfate and in 6 M guanidine hydrochloride. Values obtained are as follows: I, 47 500; II, 45 500; III, 29 500; IV, 27 800; V, 24 800; VI, 13 900; VII, 10 700; VIII, 4 800-9 00. Individual polypeptides have been purified and the amino acid composition of several of these have been determined. At least one polypeptide, the apoprotein of cytochrome b, is hydrophobic in character and this is a mitochondrially synthesized component (B. Lorenz, W. Kleinow, and H. Weiss (1974), Hoppe-Seyler's Z. Physiol. Chem. 355, 300). Other polypeptides including the hemoprotein of cytochrome c1 are more hydrophilic in amino acid composition.

Amino Acids↗
PubMed1975

The subunit structure of the cytochrome c oxidase complex.

The subunit structure of the cytochrome c oxidase complex has been obtained for three preparations each isolated by a different detergent procedure. Six polypeptides were present in all samples with the following molecular weights: subunits I, 36000; II, 22500, III, 17100; IV, 12500; V, 9700; and VI, 5300. These subunits have been purified by gel filtration in sodium dodecyl sulfate or in 6 M guanidine hydrochloride and their amino acid compositions have been determined. Subunit I is hydrophobic in character with a polarity of 35.7%. Subunits II through VI are more hydrophilic with polarities of 45.5, 48.6, 47.8, 49.7, and 53.7%, respectively.

Amino Acids↗