Organization of the genes involved in the ribulose monophosphate pathway in an obligate methylotrophic bacterium, Methylomonas aminofaciens 77a.

The 4.4-kb PstI fragment harboring the gene encoding 3-hexulose-6-phosphate synthase, rmpA, which was previously cloned from the chromosome of an obligate methylotroph, Methylomonas aminofaciens 77a, was investigated in detail. In addition to the rmpA gene, the fragment contained three open reading frames encoding transaldolase (rmpD), IS10-R (rmpI), and 6-phospho-3-hexuloisomerase (PHI) (rmpB). The rmpB gene product was overproduced in Escherichia coli cells, purified to homogeneity, and then enzymatically identified as PHI. The gene organization of the ribulose monophosphate pathway enzymes together with a transposon, IS10-R, is discussed from both evolutionary and regulatory aspects.