... cobalamins (2.9–5.1°)[9,10].Figure 4C indicates the comparison of the position of the a-acetamide side chain of pyrrole ring A of the corrin ring in the glycerol dehydratase-bound cobalamin (Fig. ... aD in the N-terminal and by three than bD in the C-terminal,respectively. In the final structure, all residues of the a chain(Met1–Glu555), all but N-terminal 10 residues of the bchain (Phe11–Glu194), ... substrate, and K+,an essential cofactor, are bound inside the barrel. The activesite-cavity is covered by the corrin ring of cobalamin that isbound on the interface of the a and b subunits....