New insights in the regulation of plant succinate dehydrogenase on the role of the protonmotive force

Affourtit, Charles, Krab, Klaas, Leach, Graeme R, Whitehouse, David G and Moore, Anthony L (2001) New insights in the regulation of plant succinate dehydrogenase on the role of the protonmotive force. Journal of Biological Chemistry, 276 (35). pp. 32567-32574. ISSN 0021-9258

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Abstract

Regulation of succinate dehydrogenase was investigated using tightly coupled potato tuber mitochondria in a novel fashion by simultaneously measuring the oxygen uptake rate and the ubiquinone (Q) reduction level. We found that the activation level of the enzyme is unambiguously reflected by the kinetic dependence of the succinate oxidation rate upon the Q-redox poise. Kinetic results indicated that succinate dehydrogenase is activated by both ATP (K ½ ~ 3 µm) and ADP. The carboxyatractyloside insensitivity of these stimulatory effects indicated that they occur at the cytoplasmic side of the mitochondrial inner membrane. Importantly, our novel approach revealed that the enzyme is also activated by oligomycin (K ½~ 16 nm). Time-resolved kinetic measurements of succinate dehydrogenase activation by succinate furthermore revealed that the activity of the enzyme is negatively affected by potassium. The succinate-induced activation (±K +) is prevented by the presence of an uncoupler. Together these results demonstrate that in vitro activity of succinate dehydrogenase is modulated by the protonmotive force. We speculate that the widely recognized activation of the enzyme by adenine nucleotides in plants is mediated in this manner. A mechanism that could account for such regulation is suggested and ramifications for its in vivo relevance are discussed.

Item Type: Article
Additional Information: Project devised and supervised by ALM and conducted in my laboratory by 2 PhD students and external collaborator (KK)Results demonstrate for the first time that succinate dehydrogenase is regulated by the protonmotive force in plant mitochondria.
Schools and Departments: School of Life Sciences > Biochemistry
Depositing User: David Whitehouse
Date Deposited: 06 Feb 2012 19:30
Last Modified: 29 Jun 2012 09:17
URI: http://sro.sussex.ac.uk/id/eprint/20884
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