The PDB entry 1BMT, it has two cobalt metal centers which appear to be symmetric
copies of each other, I have focused on one of the atoms. The cobalt is coordinated
with 6 atoms:
C: 1.956A
N (of His): 2.242
N: 2.013
N: 2.017
N: 1.924
N: 1.916
The article referenced is: Drennan,
C.L., Huang, S., Drummond, J.T., Matthews, R.G., Lidwig, M.L.: How a protein
binds b12: A 3.0A X-ray structure of B12-binding domains of methionine synthase.
Science. 266 pp. 1669 (1994).