2H4N

H94N CARBONIC ANHYDRASE II COMPLEXED WITH ACETAZOLAMIDE

2H4N の概要

• エントリーDOI: 10.2210/pdb2h4n/pdb
• 分子名称: CARBONIC ANHYDRASE II, ZINC ION, 5-ACETAMIDO-1,3,4-THIADIAZOLE-2-SULFONAMIDE, ... (4 entities in total)
• 機能のキーワード: lyase, oxo-acid, acetylation
• 由来する生物種: Homo sapiens (human)
• 細胞内の位置: Cytoplasm: P00918
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 29486.88

構造登録者

Lesburg, C.A.,Christianson, D.W. (登録日: 1997-05-29, 公開日: 1997-09-17, 最終更新日: 2024-05-29)

主引用文献

Lesburg, C.A.,Huang, C.,Christianson, D.W.,Fierke, C.A.
Histidine --> carboxamide ligand substitutions in the zinc binding site of carbonic anhydrase II alter metal coordination geometry but retain catalytic activity.
Biochemistry, 36:15780-15791, 1997

PubMed Abstract: The catalytic zinc ion of human carbonic anhydrase II (CAII) is coordinated by three histidine ligands (H94, H96, and H119) and a hydroxide ion with tetrahedral geometry. Structural and functional analysis of variants in which the zinc ligands H94 and H119 are substituted with asparagine and glutamine, and comparison with results obtained with aspartate and glutamate substitutions indicate that the neutral ligand field provided by the protein optimizes the electrostatic environment for the catalytic function of the metal ion, including stabilization of bound anions. This is demonstrated by catalytic activity measurements for ester hydrolysis and CO2 hydration, as well as sulfonamide inhibitor affinity assays. High-resolution X-ray crystal structure determinations of H94N, H119N, and H119Q CAIIs reveal that the engineered carboxamide side chains coordinate to zinc with optimal stereochemistry. However, zinc coordination geometry remains tetrahedral only in H119Q CAII. Metal geometry changes to trigonal bipyramidal in H119N CAII due to the addition of a second water molecule to the zinc coordination polyhedron and also in H94N CAII due to the displacement of zinc-bound hydroxide by the bidentate coordination of a Tris molecule. Possibly, the bulky histidine imidazole ligands of the native enzyme play a role in disfavoring trigonal bipyramidal coordination geometry for zinc. Protein-metal affinity is significantly compromised by all histidine --> carboxamide ligand substitutions. Diminished affinity may result from significant movements (up to 1 A) of the metal ion from its position in the wild-type enzyme, as well as the associated, minor conformational changes of metal ligands and their neighboring residues.

PubMed: 9398308
DOI: 10.1021/bi971296x

実験手法

X-RAY DIFFRACTION (1.9 Å)