Catalyzes cobalt insertion in the corrin ring. ATP + Co(2+) + H2O + hydrogenobyrinate a,c-diamide = ADP + cob(II)yrinate a,c diamide + 5 H(+) + phosphate Cofactor biosynthesis; adenosylcobalamin biosynthesis; cob(II)yrinate a,c-diamide from precorrin-2 (aerobic route): step 10/10. Heterotrimer of CobN, CobS and CobT. Was originally thought to originate from Pseudomonas denitrificans, but similarity searches show that the sequence is much closer to Sinorhizobium. The entry's taxonomy has been changed.