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Low reserve of cytochrome c oxidase capacity in vivo in the respiratory chain of a variety of human cell types

Villani, Gaetano and Greco, Marilena and Papai, Sergio and Attardi, Giuseppe (1998) Low reserve of cytochrome c oxidase capacity in vivo in the respiratory chain of a variety of human cell types. Journal of Biological Chemistry, 273 (48). pp. 31829-31836. ISSN 0021-9258.

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The question of whether and to what extent the in vivo cytochrome c oxidase (COX) capacity in mammalian cells exceeds that required to support respiration is still unresolved. In the present work, to address this question, a newly developed approach for measuring the rate of COX activity, either as an isolated step or as a respiratory chain-integrated step, has been applied to a variety of human cell types, including several tumor-derived semidifferentiated cell lines, as well as specialized cells removed from the organism. KCN titration assays, carried out on intact uncoupled cells, have clearly shown that the COX capacity is in low excess (16-40%) with respect to that required to support the endogenous respiration rate. Furthermore, measurements of O2 consumption rate supported by 0.4 mM tetramethyl-p-phenylenediamine in antimycin-inhibited uncoupled intact cells have given results that are fully consistent with those obtained in the KCN titration experiments. Similarly, KCN titration assays on digitonin-permeabilized cells have revealed a COX capacity that is nearly limiting (7-22% excess) for ADP + glutamate/malate-dependent respiration. The present observations, therefore, substantiate the conclusion that the in vivo control of respiration by COX is much tighter than has been generally assumed on the basis of experiments carried out on isolated mitochondria. This conclusion has important implications for understanding the role of physiological or pathological factors in affecting the COX threshold.

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Additional Information:Copyright © 1998 by The American Society for Biochemistry and Molecular Biology, Inc. Received for publication, July 27, 1998, and in revised form, September 1, 1998. We are grateful to Dr. N. Capitanio for helpful discussions and for critical reading of the manuscript, and we thank B. Keeley, A. Drew, and R. Zedan for technical assistance. These investigations were supported by National Institutes of Health Grant GM-11726 (to G.A.), Grant 97.01167.P.F.49 “Biotechnologies” of the Italian Research Council, and a grant from the Italian Project for Bioenergetics and Membrane Transport of Ministero dell’ Università e della Ricerca Scientifica e Tecnologica, Italy (to S.P.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Issue or Number:48
Record Number:CaltechAUTHORS:VILjbc98
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:6097
Deposited By: Lindsay Cleary
Deposited On:28 Nov 2006
Last Modified:02 Oct 2019 23:29

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