Abstract
In chloroplasts, Fd forms an electron transfer complex with redox enzymes, such as Fd:NADP+ oxidoreductase(FNR), sulfite reductase, nitrite reductase and glutamate synthase. Fd therefore influences redox metabolism through the formation of intermolecular electron transfer complexes, and these are the subject of our research.
Two maize leaf FNR isozymes;L-FNR1 and L-FNR2, have previously been described and we have also identified a new L-FNR. Chloroplast fractionation revealed L-FNR1 was located at the thylakoid membrane, new L-FNR in the stroma and L-FNR2 in both fractions. Using Fd-affinity chromatography with wild type and mutant Fd-resin columns we found interaction of different FNR isoenzymes strongly depend on specific Fd amino acid residues. Therefore, despite very high sequence homology, these L-FNR isoenzymes vary dramatically in location and Fd interaction.
