NADH binding site, complex

Fig. 3.13. Complex I. A, the map shows how Complex I can be dissected into subcomplexes. Treatment with chaotropic agents splits the Complex into three fractions an iron-sulphur protein (ISP), a flavoprotein (NADH dehydrogenase) complex, and a hydrophobic residue. The figure shows the polypeptide composition and the flavin and iron content of these subcomplexes. ISP can be further split into three FeS-containing fractions by trichloroacetate. See text for details and references. B, the topography of the components mapped in A has been studied by Ragan et al. [290,296]. The NADH-binding site is in the flavoprotein fraction [297]. This, as well as the FeS protein complex (ISP), are possibly buried in the membrane and shielded from phospholipids by the hydrophobic residue (HR). Adapted from Refs. 290, 296.

Friedrich, T., VanHeek, P., Leif, H., Ohnishi, T., Forche, E., Kunze, B., Jansen, R., Trowitzsch-Kienast, W., Holfe, G., Reichenbach, H., and Weiss, H. Two binding sites of inhibitors in NADH ubiquinone oxidoreductase (complex I) relationship of one site with the ubiquinone oxido-reductase. Eur. J. Biochem., 219, 691, 1994. 

The means by which NAD affects the oxidation of NADH is still uncertain. The evidence for two pyridine nucleotide binding sites is not compelling. The alternative explanation that NAD functions by reversing the equilibrium between EHj and 4-electron-reduced enzyme (EH4) is shown in Eq. (9). There is some kinetic evidence for a dead end complex... 

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