Crystallographic Studies of the Binding of Ligands to theDicarboxylate Site of Complex II, and the Identity of the Ligand in the'Oxaloacetate-Inhibited' State
Mitochondrial Complex II (succinate:ubiquinoneoxidoreductase) is purified in a partially innactivated state, which canbe activated by removal of tightly bound oxaloacetate (Kearney, E.B. etal. Biochem Biophys Res Commun 49, 1115-1121). We crystallized Complex IIin the presence of oxaloacetate or with the endogenous inhibitor bound.The structure showed a ligand essentially identical to the "malate-likeintermediate" found in Shewanella Flavocytochrome c crystallized withfumarate (Taylor, P., et al. Nat Struct Biol 6, 1108-1112.)Crystallization of Complex II in the presence of excess fumarate alsogave the malate-like intermediate or a mixture of that and fumarate atthe active site. In order to more conveniently monitor the occupationstate of the dicarboxylate site, we are developing a library of UV/Visspectral effects induced by binding different ligands to the site.Treatment with fumarate results in rapid development of the fumaratedifference spectrum and then a very slow conversion into a speciesspectrally similar to the OAA liganded complex. Complex II is known to becapable of oxidizing malate to the enol form of oxaloacetate (Belikova,Y.O., et al. Biochim Biophys Acta 936, 1-9). The observations abovesuggest it may also be capable of interconverting fumarate and malate. Itmay be useful for understanding the mechanism and regulation of theenzyme to identify the malate-like intermediate and its pathway offormation from oxaloacetate or fumarate.
- Research Organization:
- Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
- Sponsoring Organization:
- USDOE Director, Office of Science; National Institutes ofHealth
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 903131
- Report Number(s):
- LBNL--60941; BnR: 400412000
- Journal Information:
- Biochimica Biophysica Acta-Bioenergetics, Journal Name: Biochimica Biophysica Acta-Bioenergetics Journal Issue: 9-10 Vol. 1757
- Country of Publication:
- United States
- Language:
- English
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