1CAH

STRUCTURE OF COBALT CARBONIC ANHYDRASE COMPLEXED WITH BICARBONATE

Summary for 1CAH

• Entry DOI: 10.2210/pdb1cah/pdb
• Descriptor: CARBONIC ANHYDRASE II, COBALT (II) ION, BICARBONATE ION, ... (4 entities in total)
• Functional Keywords: lyase(oxo-acid)
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm : P00918
• Total number of polymer chains: 1
• Total formula weight: 29277.81

Authors

Hakansson, K.,Wehnert, A. (deposition date: 1992-06-25, release date: 1993-10-31, Last modification date: 2024-02-07)

Primary citation

Hakansson, K.,Wehnert, A.
Structure of cobalt carbonic anhydrase complexed with bicarbonate.
J.Mol.Biol., 228:1212-1218, 1992

PubMed Abstract: The three-dimensional structure of a complex between catalytically active cobalt(II) substituted human carbonic anhydrase II and its substrate bicarbonate was determined by X-ray crystallography (1.9 A). One water molecule and two bicarbonate oxygen atoms are found at distances between 2.3 and 2.5 A from the cobalt ion in addition to the three histidyl ligands contributed by the peptide chain. The tetrahedral geometry around the metal ion in the native enzyme with a single water molecule 2.0 A from the metal is therefore lost. The geometry is difficult to classify but might best be described as distorted octahedral. The structure is suggested to represent a water-bicarbonate exchange state relevant also for native carbonic anhydrase, where the two unprotonized oxygen atoms of the substrate are bound in a carboxylate binding site and the hydroxyl group is free to move closer to the metal thereby replacing the metal-bound water molecule. A reaction mechanism based on crystallographically determined enzyme-ligand complexes is represented.

PubMed: 1474587
DOI: 10.1016/0022-2836(92)90327-G

Experimental method

X-RAY DIFFRACTION (1.88 Å)