1CVB

STRUCTURAL AND FUNCTIONAL IMPORTANCE OF A CONSERVED HYDROGEN BOND NETWORK IN HUMAN CARBONIC ANHYDRASE II

1CVB の概要

• エントリーDOI: 10.2210/pdb1cvb/pdb
• 分子名称: CARBONIC ANHYDRASE II, ZINC ION, SULFATE ION, ... (4 entities in total)
• 機能のキーワード: lyase(oxo-acid)
• 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: 29317.36

構造登録者

Ippolito, J.A.,Christianson, D.W. (登録日: 1993-02-04, 公開日: 1993-10-31, 最終更新日: 2024-02-07)

主引用文献

Krebs, J.F.,Ippolito, J.A.,Christianson, D.W.,Fierke, C.A.
Structural and functional importance of a conserved hydrogen bond network in human carbonic anhydrase II.
J.Biol.Chem., 268:27458-27466, 1993

PubMed Abstract: Amino acid substitutions at Thr199 of human carbonic anhydrase II (CAII) (Thr199-->Ser, Ala, Val, and Pro) were characterized to investigate the importance of a conserved hydrogen bonding network. The three-dimensional structures of azide-bound and sulfate-bound T199V CAIIs were determined by x-ray crystallographic methods at 2.25 and 2.4 A, respectively (final crystallographic R factors are 0.173 and 0.174, respectively). The CO2 hydrase activities of T199S and T199P variants suggest that the side chain methyl and backbone amino functionalities stabilize the transition state by approximately 0.4 and 0.8 kcal/mol, respectively. The side chain hydroxyl group causes: stabilization of zinc-hydroxide relative to zinc-water (pKa increases approximately 2 units); stabilization of the transition state for bicarbonate dehydration relative to the CAII.HCO3- complex (approximately 5 kcal/mol); and destabilization of the CAII.HCO3- complex (approximately 0.8 kcal/mol). An inverse correlation between log(kcatCO2/KM) and the pKa of zinc-water (r = 0.95, slope = -1) indicates that the hydrogen bonding network stabilizes the chemical transition state and zinc-hydroxide similarly. These data are consistent with the hydroxyl group of Thr199 forming a hydrogen bond with the transition state and a non-hydrogen-bonded van der Waals contact with CAII.HCO3-.

PubMed: 8262987

実験手法

X-RAY DIFFRACTION (2.4 Å)