Expression of rat liver AdoHcy hydrolase in a Rhodobacter capsulatus ahcY mutant restores pigment formation and photosynthetic growth.

An amino acid alignment of fourteen S-adenosylhomocysteine hydrolases shows that sequences from six photosynthetic species and one species possibly derived from algae have an internal 36 to 41 amino acid sequence that is not present in hydrolase sequences from seven non-photosynthetic species. In the photosynthetic eubacterium Rhodobacter capsulatus, the StLB1 strain has a disrupted hydrolase gene, and hydrolase activity is not detectable. Photopigment synthesis and photosynthetic growth are significantly reduced in the StLB1 strain. Introduction of rat hydrolase cDNA into the StLB1 strain restored hydrolase activity, photopigment synthesis and photosynthetic growth. The results show that the 36 amino acid sequence of Rhodobacter capsulatus S-adenosylhomocysteine hydrolase does not have a photosynthesis specific function.