Identification of pigments in mutants lacking bchX, bchY, or bchZ gene of purple bacteria, Rubrivivax gelatinosus

Abstract

In bacteriochlorophyll-biosynthesis, bchX, bchY, and bchZ genes have been suggested to be responsible for saturation of RingΙΙ of the porphyrin ring. The amino acid sequence of BchX resembles to that of BchL, a subunit of the enzyme working in RingIV saturation, BchY and BchZ are corresponding to BchN and BchB of this enzyme, respectively. Although BchL, N, and B are known to serve as a complex, it hasn^'t been shown whether BchX, Y, and Z form a complex. We constructed three mutants lacking bchX, bchY, and bchZ, respectively, and analyzed pigments accumulated in these mutants. All of the mutants grown under semi-aerobic conditions accumulated same pigments with a similar ratio. By MALDI-TOF, compounds derived from chlorophyllide a and 3-devinyl-3-hydroxyetyl chlorophyllide a were detected. Significant accumulation of chlorophyllide a derivatives suggested that the saturation of RingΙΙ by BchX, Y, Z precedes hydroxylation of vinyl-group of RingI.