Abstract
Bacteriochlorophyll a has bacteriochlorin ring structure that isformed by the sequential actions of two nitrogenase-like enzymes,dark-operative protochlorophyllide reductase (DPOR) and chlorophyllide a reductase (COR). We previously demonstrated that DPOR consists of two components, L-protein and NB-protein, and COR also does of two components, X-protein and YZ-protein, which are structurally related to nitrogenase Fe-protein and MoFe-protein,respectively. Here we report biochemical properties of two components, NB-protein and YZ-protein. Purified NB-protein and YZ-protein were found to bind the substrates, protochlorophyllide and chlorophyllide, respectively, indicating that both are the catalytic components. Dithionite-reduced YZ-protein showed an EPR signal with g-values of 2.04, 1.94 and 1.92. While dithionite-reduced NB-protein was EPR silent, an EPR signal with g-values of 1.94 and 1.92 was detected in the presence of L-protein and ATP. These results suggested that NB-protein and YZ-protein carry in common [4Fe-4S] clusters with different properties rather than the complex clusters of MoFe-protein.
