Primary structure, expression in Escherichia coli, and properties of S-adenosyl-L-methionine:uroporphyrinogen III methyltransferase from Bacillus megaterium

A Bacillus megaterium DNA fragment encoding S-adenosyl-L-methionine:uroporphyrinogen III methyltransferase (SUMT) activity was subcloned and sequenced. The encoded polypeptide showed more than 43.5% strict homology to Pseudomonas denitrificans SUMT (F. Blanche, L. Debussche, D. Thibaut, J. Crouzet, and B. Cameron, J. Bacteriol. 171:4222-4231, 1989). The B. megaterium polypeptide was overexpressed in Escherichia coli, partially purified, and shown to exhibit, like P. denitrificans SUMT, substrate inhibition at uroporphyrinogen III concentrations above 0.5 microM, suggesting a common regulation for aerobic cobalamin-producing organisms.