The multiple nicotinamide nucleotideâbinding subunits of bovine heart mitochondrial NADH:ubiquinone oxidoreductase (complex I)
2000
Yamaguchi, Mutsuo | Belogrudov, Grigory I. | MatsunoâYagi, Akemi | Hatefi, Youssef
Direct photoaffinity labeling of purified bovine heart NADH:ubiquinone oxidoreductase (complexâI) with 32Pâlabeled NAD(H), NADP(H) and ADP has shown that five polypeptides become labeled, with molecular masses of 51, 42, 39, 30, and 18–20âkDa. The 51 and the 30âkDa polypeptides were labeled with either [32P]NAD(H), [32P]NADP(H) or [βâ32P]ADP. The 42âkDa polypeptide was labeled with [32P]NAD(H) and to a small extent with [βâ32P]ADP. It was not labeled with [32P]NADP(H). The 39âkDa polypeptide was labeled with [32P]NADPH and to a small extent with [βâ32P]ADP. Our previous studies had shown that this subunit also binds NADP, but not NAD(H) [Yamaguchi, M., Belogrudov, G.I. & Hatefi, Y. (1998) J. Biol. Chem.273, 8094–8098]. The 18–20âkDa polypeptide was labeled only with [32P]NADPH. Among these polypeptides, the 51âkDa subunit is known to contain FMN and a [4Fe–4S] cluster, and is the NAD(P)Hâbinding subunit of the primary dehydrogenase domain of complexâI. The possible roles of the other nucleotideâbinding subunits of complexâI have been discussed.
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