3KOI
Crystal structure of cobalt (III) human carbonic anhydrase II at pH 6.0
Summary for 3KOI
| Entry DOI | 10.2210/pdb3koi/pdb |
| Related | 3KOK 3KON 3KS3 |
| Descriptor | Carbonic anhydrase 2, COBALT (III) ION (3 entities in total) |
| Functional Keywords | carbonic anhydrase, metalloenzyme, cobalt substitution, crystal ph, lyase |
| Biological source | Homo sapiens (human) |
| Cellular location | Cytoplasm: P00918 |
| Total number of polymer chains | 1 |
| Total formula weight | 29348.00 |
| Authors | Avvaru, B.S. (deposition date: 2009-11-13, release date: 2010-08-25, Last modification date: 2024-02-21) |
| Primary citation | Avvaru, B.S.,Arenas, D.J.,Tu, C.,Tanner, D.B.,McKenna, R.,Silverman, D.N. Comparison of solution and crystal properties of Co(II)-substituted human carbonic anhydrase II. Arch.Biochem.Biophys., 502:53-59, 2010 Cited by PubMed Abstract: The visible absorption of crystals of Co(II)-substituted human carbonic anhydrase II (Co(II)-HCA II) were measured over a pH range of 6.0-11.0 giving an estimate of pK(a) 8.4 for the ionization of the metal-bound water in the crystal. This is higher by about 1.2 pK(a) units than the pK(a) near 7.2 for Co(II)-CA II in solution. This effect is attributed to a nonspecific ionic strength effect of 1.4M citrate in the precipitant solution used in the crystal growth. A pK(a) of 8.3 for the aqueous ligand of the cobalt was measured for Co(II)-HCA II in solution containing 0.8M citrate. Citrate is not an inhibitor of the catalytic activity of Co(II)-HCA II and was not observed in crystal structures. The X-ray structures at 1.5-1.6A resolution of Co(II)-HCA II were determined for crystals prepared at pH 6.0, 8.5 and 11.0 and revealed no conformational changes of amino-acid side chains as a result of the use of citrate. However, the studies of Co(II)-HCA II did reveal a change in metal coordination from tetrahedral at pH 11 to a coordination consistent with a mixed population of both tetrahedral and penta-coordinate at pH 8.5 to an octahedral geometry characteristic of the oxidized enzyme Co(III)-HCA II at pH 6.0. PubMed: 20637176DOI: 10.1016/j.abb.2010.07.010 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (1.64 Å) |
Structure validation
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