Abstract
The GGR has been supposed to reduce three of four double bonds of a geranylgeranyl (GG) group at the C-17 position of (bacterio)chlorophyll((B)Chl)s and produce a phytyl (P) group. We expressed cyanobacterial and purple bacterial GGR genes (chlP and bchP genes, respectively) in the GGR-inactivated mutant of the green sulfur bacterium Chlorobaculum tepidum, whose mutant accumulated geranylgeranylated Chl a (Chl aGG) and BChl a (BChl aGG). The chlP-incorporated cells accumulated BChl aP as well as intermediates synthesized during the reduction process of double bonds in the GG group of BChl aGG in addition to Chl aP. From the HPLC analysis, the order of the reductions was found to be the same as BChl aGG in purple bacteria, as reported previously. While, in the bchP cells, Chl aP as well as intermediates synthesized during the reduction process of of Chl aGG was accumulated in addition to BChl aP. However, it was revealed that the order of the reduction process of the GG group bound to Chl a was different from that of BChl aGG. We will discuss specific properties of GGRs from different photosynthetic bacteria in terms of the reduction process of a GG group.
