Oxygenic photosynthesis-specific subunits of cyanobacterial NADPH dehydrogenases.

Cyanobacterial NADPH dehydrogenase (NDH-1) or NDH-1-like complex is localized in the thylakoid membrane and participates in a variety of bioenergetic reactions, including respiration, cyclic electron transport around photosystem I and CO2 uptake. Over the past decade, a significant achievement has been made in identifying seven oxygenic photosynthesis-specific (OPS) subunits of NDH-1 enzyme, NdhL to NdhQ and NdhS, in several cyanobacterial strains. Six of them are also found in higher plants but not in nonphototrophs. This indicates an exclusive existence of these OPS Ndh subunits in oxygenic photosynthetic organisms and suggested certain role of cyanobacterial and chloroplastic NDH-1 in photosynthetic reactions. In this review, we describe these seven OPS subunits of cyanobacterial NDH-1, focusing on their identification, localization, function, and evolution from cyanobacteria to higher plants. A crucial role of these OPS subunits on the function of cyanobacterial NDH-1 is proposed.