Abstract
The CP12 from higher plants, eukaryotic algae, and Synechocystis PCC6803 contained four cysteine (Cys) residues essential for the formation of two peptide loops. However, the CP12 from Synechococcus PCC7942 lacked the two Cys residues involved in the formation of the N-terminal peptide loop. When the crude extract of S. 7942 containing 100 μM NAD+ was subjected to gel filtration, CP12, GAPDH, and PRK were obtained as high-molecular mass aggregates. The ratio of NADP(H):NAD(H) in S. 7942 cells under light and dark conditions were 6.5:1 and 3.8:1, respectively. These data suggest that the reversible dissociation of GAPDH/CP12/PRK complex is mediated by the change of NADP(H):NAD(H) ratio under light/dark conditions. To analyze the molecular interaction between CP12 and GAPDH or PRK, we are constructing the CP12 mutant changed Cys residues (61 and 70) to Ser residue that are associated with the formation the C-terminal peptide loop.
