EVIDENCE FOR AN ASSOCIATION OF NDH-B, NDH-J GENE-PRODUCTS AND FERREDOXIN-NADP-REDUCTASE AS COMPONENTS OF A CHLOROPLASTIC NAD(P)H DEHYDROGENASE COMPLEX

Using non-denaturing gel electrophoresis and staining with nitro-blue tetrazolium, me reveal the presence of two NAD(P)H oxidoreductase acti vity bands within thylakoids membranes of Solanum tuberosum L. Second dimension SDS-PAGE and Western analysis show that one of the activity bands contains several polypeptides, two of them being recognized by a ntibodies directed against peptides corresponding to conserved domains of chloroplastic genes products NDH B and NDH J (at 32 and 18 kDa, re spectively). Both activity bands also contain a polypeptide (around 36 kDa) recognized by an antibody directed against ferredoxin-NADP(+)-re ductase (FNR). We conclude from these results that both chloroplastic ndh B and ndh J gene products are components of a thylakoid NAD(P)H de hydrogenase complex. The association with FNR is suggested to allow th e complex to use NADPH instead of NADH as a preferential substrate.