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PDBsum entry 1koq

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Lyase PDB id
1koq
Jmol
Contents
Protein chains
222 a.a. *
Metals
_ZN ×2
Waters ×147
* Residue conservation analysis

References listed in PDB file
Key reference
Title Crystal structure of carbonic anhydrase from neisseria gonorrhoeae and its complex with the inhibitor acetazolamide.
Authors S.Huang, Y.Xue, E.Sauer-Eriksson, L.Chirica, S.Lindskog, B.H.Jonsson.
Ref. J Mol Biol, 1998, 283, 301-310. [DOI no: 10.1006/jmbi.1998.2077]
PubMed id 9761692
Abstract
The crystal structure of carbonic anhydrase from Neisseria gonorrhoeae has been solved to a resolution of 1.78 A by molecular replacement using human carbonic anhydrase II as a template. After refinement the R factor was 17.8% (Rfree=23.2%). There are two molecules per asymmetric unit (space group P21), but they have essentially identical structures. The fold of the N. gonorrhoeae enzyme is very similar to that of human isozyme II; 192 residues, 74 of which are identical in the two enzymes, have equivalent positions in the three-dimensional structures. This corresponds to 85% of the entire polypeptide chain of the bacterial enzyme. The only two cysteine residues in the bacterial enzyme, which has a periplasmic location in the cell, are connected by a disulfide bond. Most of the secondary structure elements present in human isozyme II are retained in N. gonorrhoeae carbonic anhydrase, but there are also differences, particularly in the few helical regions. Long deletions in the bacterial enzyme relative to human isozyme II have resulted in a considerable shortening of three surface loops. One of these deletions, corresponding to residues 128 to 139 in the human enzyme, leads to a widening of the entrance to the hydrophobic part of the active site cavity. Practically all the amino acid residues in the active site of human isozyme II are conserved in the N. gonorrhoeae enzyme and have similar structural positions. However, the imidazole ring of a histidine residue, which has been shown to function as a proton shuttle in the catalytic mechanism of the human enzyme, interacts with an extraneous entity, which has tentatively been identified as a 2-mercaptoethanol molecule from the crystallization medium. When this entity is removed by soaking the crystal in a different medium, the side-chain of His66 becomes quite mobile. The structure of a complex with the sulfonamide inhibitor, acetazolamide, has also been determined. Its position in the active site is very similar to that observed in human carbonic anhydrase II.
Figure 2.
Figure 2. Schematic drawings of the structures of NGCA (left) and HCA II (right). The molecules are shown in a slightly different orientation from that in Figure 1. The N termini are in the upper left parts of the drawings. The zinc ions are shown as filled circles. Arrows indicate the three loops in HCA II which are deleted in NGCA. The Figure was produced with MOLSCRIPT [Kraulis 1991].
Figure 4.
Figure 4. Stereo diagram showing the Cys28---Cys181 disulfide bond in NGCA. Thin lines represent the corresponding residues in HCA II.
The above figures are reprinted by permission from Elsevier: J Mol Biol (1998, 283, 301-310) copyright 1998.
Secondary reference #1
Title The complete sequence, Expression in escherichia coli, Purification and some properties of carbonic anhydrase from neisseria gonorrhoeae.
Authors L.C.Chiric─â, B.Elleby, B.H.Jonsson, S.Lindskog.
Ref. Eur J Biochem, 1997, 244, 755-760.
PubMed id 9108244
Abstract
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