Abstract
Dark-operative protochlorophyllide oxidoreductase (DPOR) is a nitrogenase-like enzyme catalyzing D-ring reduction of protochlorophyllide to form chlorophyllide. DPOR consists of two components, L-protein and NB-proteins, which are structurally related to nitrogenase Fe-protein and MoFe-protein, respectively. Because functional expression of nitrogenase components requires a set of proteins unique in nitrogen-fixing organisms for assemble of metallocenters and maturation of the components, nitrogenase components are not expressed as active forms in conventional expression system of Escherichia coli. There has been no report examining if active DPOR components are expressed in E. coli due to the absence of reliable assay system. Here we report the successful functional expression of DPOR components in E. coli, which was evaluated by the assay system of Rhodobacter capsulatus. The results suggested that a set of proteins in E. coli supports assemble of metallocenters and maturation of DPOR components, which is different from nitrogenase components.
