期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1807, 期 3, 页码 286-292出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2010.12.008
关键词
NADH dehydrogenase; NADH:quinone oxidoreductase; Respiratory chain; Sodium/proton antiporter
资金
- FCT [REDE/1517/RMN/2005, REEQ/336/BIO/2005, SFRH/BD/25288/2005, POCI/QUI-BIQ/100302/2008]
- Fundação para a Ciência e a Tecnologia [SFRH/BD/25288/2005] Funding Source: FCT
The nature of the ions that are translocated by Escherichia coli and Paracoccus denitrificans complexes I was investigated. We observed that E. coli complex I was capable of proton translocation in the same direction to the established Delta Psi, showing that in the tested conditions, the coupling ion is the H+ Furthermore, Na+ transport to the opposite direction was also observed, and, although Na+ was not necessary for the catalytic or proton transport activities, its presence increased the latter. We also observed H+ translocation by P. denitrificans complex I, but in this case, H+ transport was not influenced by Na+ and also Na+ transport was not observed. We concluded that E. coli complex I has two energy coupling sites (one Na+ independent and the other Na+ dependent), as previously observed for Rhodothermus marinus complex I. whereas the coupling mechanism of P. denitrificans enzyme is completely Na+ independent. This work thus shows that complex I energy transduction by proton pumping and Na+/H+ antiporting is not exclusive of the R. marinus enzyme. Nevertheless, the Na+/H+ antiport activity seems not to be a general property of complex I, which may be correlated with the metabolic characteristics of the organisms. (C) 2010 Elsevier B.V. All rights reserved.
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