E coli BTUF, the periplasmic binding protein for vitamin B12

PDB entry 1N4A - N.K KARPOWICH,P.C.SMITH,J.F.HUNT (11-Mar-2003) with coordination bond to Co added
(page prepared by BB from Chem 351, Spring 2004)
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Cruiser Index

The PDB code is 1N4A, it has a cobalt as the metal center which is coordinated to 6 atoms:
N (not in the porphyrin): 2.162A
C: 1.949A
looking down the Co-C bond the following are the nitrogens going around clockwise beginning with the one with the bond not showing
N: 1.919A
N: 1.895A
N: 1.884A
N: 1.940A
The article referenced is: Karpowich, N. K., Huang, H. H., Smith, P. C., Hunt, J. F.: Crystal Structures of the Btuf Periplasmic Binding Protein for Vitamin B12 Suggest a Functionally Important Reduction in Protein Mobility Upon Ligand Binding J.Biol.Chem. 278 pp. 8429 (2003)