Accommodation of NO in the active site of mammalian and bacterial cytochrome c oxidase aa3

Abstract : Following different reports on the stoichiometry and configuration of NO binding to mammalian and bacterial reduced cytochrome c oxidase aa3 (CcO), we investigated NO binding and dynamics in the active site of beef heart CcO as a function of NO concentration, using ultrafast transient absorption and EPR spectroscopy. We find that in the physiological range only one NO molecule binds to heme a3, and time-resolved experiments indicate that even transient binding to CuB does not occur. Only at very high (∼ 2 mM) concentrations a second NO is accommodated in the active site, although in a different configuration than previously observed for CcO from Paracoccus denitrificans [E. Pilet, W. Nitschke, F. Rappaport, T. Soulimane, J.-C. Lambry, U. Liebl and M.H. Vos. Biochemistry 43 (2004) 14118-14127], where we proposed that a second NO does bind to CuB. In addition, in the bacterial enzyme two NO molecules can bind already at NO concentrations of ∼ 1 μM. The unexpected differences highlighted in this study may relate to differences in the physiological relevance of the CcO-NO interactions in both species.
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Submitted on : Wednesday, September 24, 2008 - 4:44:38 PM
Last modification on : Thursday, February 7, 2019 - 4:33:00 PM

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Eric Pilet, Wolfgang Nitschke, Ursula Liebl, Marten Vos. Accommodation of NO in the active site of mammalian and bacterial cytochrome c oxidase aa3. Biochimica et Biophysica Acta (BBA) - Reviews on Bioenergetics, Elsevier, 2007, 1767 (5), pp.387-392. ⟨10.1016/j.bbabio.2007.03.001⟩. ⟨hal-00324353⟩

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