Abstract
The reaction center (RC) complex of green sulfur bacteria consists of four subunits, PscA (core homodimer), PscB (FA/FB protein), PscC (cytochrome cZ) and PscD subunit (a 17-kDa polypeptides of unknown function). To ascertain the function of PscD, we constructed a mutant lacking the PscD subunit in Chlorobium tepidum. This is the first-time achievement of the direct mutagenesis in the RC complex of green sulfur bacteria.
Kinetics of the fluorescence showed that the bacteriochlorophyll a fluorescence in the mutant decayed slower compared to that in the wild type. This result suggested that the efficiency of energy transfer from the FMO protein to the RC decreased in the mutant because of the lack of PscD. Our interpretation could be supported by the previous study of the three-dimensional imaging analysis of the Chlorobium RC complex which speculated the direct contact of PscD with the FMO protein.
