Abstract :
The photosynthetic bacterium Rhodobacter sphaeroides serves as model to study magnesium-protoporphyrin chelatase present in the branch point of the heme and bacterio chlorophyll biosynthetic pathways. The bchH, -I, and -D genes expressed in Escherichia coli from R. sphaeroides catalyze the introduction of Mg into protoporphyrin IX in an ATP-dependent manner. Thus, the three genes are involved in the Mg chelatase step in bacterio chlorophyll biosynthesis.