The puf B,A,L,M Genes are Not Sufficient to Restore the Photosynthetic Plus Phenotype to a puf L,M,X Deletion Strain

Abstract

The purple non-sulfur bacterium Rhodobacter sphaeroides has the capacity to thrive as an anaerobic phototroph. The ability to convert light energy into chemical energy within the cell is driven by a photosynthetic unit consisting of two light-harvesting antennae complexes and a reaction center (RC). The light-harvesting complexes have been labelled LHI and LHII based on their respective single (875 nm) and double (800–850 nm)infrared absorption maxima. The RC responsible for the primary light driven electron transfer is composed of three protein subunits H, M and L and contains 4 molecules of bacteriochlorophyll a (Bchl a), 2 molecules of bacteriopheophytin a, one non-heme iron and two molecules of ubi-quinone. Two of the Bchl a molecules are monomeric and are referred to as the voyeur Bchl while the other two form a dimer, or so-called special pair (1). The RC special pair undergoes a reversible photobleaching that can be measured at 860 nm or 600 nm. These two maxima have been assigned to the Q_y and Q_x transition bands of the special pair, respectively (2).