Catalyzes the two successive C-2 and C-7 methylation reactions involved in the conversion of uroporphyrinogen III to precorrin-2 via the intermediate formation of precorrin-1. It is a step in the biosynthesis of both cobalamin (vitamin B12) and coenzyme F430. 2 S-adenosyl-L-methionine + uroporphyrinogen III = H(+) + precorrin-2 + 2 S-adenosyl-L-homocysteine S-adenosyl-L-methionine + uroporphyrinogen III = H(+) + precorrin-1 + S-adenosyl-L-homocysteine precorrin-1 + S-adenosyl-L-methionine = precorrin-2 + S-adenosyl-L-homocysteine Does not show substrate inhibition at uroporphyrinogen III concentrations of up to 20 uM, in contrast to SUMT from Sinorhizobium (previously believed to be P.denitrificans). Cofactor biosynthesis; adenosylcobalamin biosynthesis; precorrin-2 from uroporphyrinogen III: step 1/1. Homodimer. Belongs to the precorrin methyltransferase family.