Nucleotide sequences of genes coding for photosynthetic reaction centers and light-harvesting proteins of Acidiphilium rubrum and related aerobic acidophilic bacteria.

The nucleotide sequences of the puf operons of the Zn-bacteriochlorophyll a (Zn-BChl a)-containing photosynthetic aerobic bacteria, Acidiphilium rubrum and Acidiphilium angustum, were determined. The nucleotide sequences of the pufL and -M of Acidiphilium cryptum, Acidiphilium multivorum, and Acidiphilium organovorum were also determined. The puf operons of A. rubrum and A. angustum contained pufB, -A, -L, -M, and -C as seen in other purple bacteria with an unknown gene directly upstream of pufB. Comparing the deduced amino acid sequences of the puf genes of the Acidiphilium species with those of other purple bacteria showed that His L168, which is highly conserved in other bacteria, is replaced by a glutamic acid in the Acidiphilium species. The three-dimensional structures of the reaction centers of Blastochloris (Rhodopseudomonas) viridis and Rhodobacter sphaeroides suggest that this residue locates closely to a special pair of bacteriochlorophylls and may be involved in the stabilization and function of "Zn-BChl a". The relative content of charged amino acid residues in the L and M subunit is a little lower in A. rubrum (10% of total) than in B. viridis (12%), and the tendency is more pronounced in the cytochrome subunit: 12.5% in A. rubrum and 18.8% in B. viridis.