4Q49

Room temperature neutron crystal structure of apo human carbonic anhydrase at pH 7.5

4Q49 の概要

• エントリーDOI: 10.2210/pdb4q49/pdb
• 分子名称: Carbonic anhydrase 2, ZINC ION (3 entities in total)
• 機能のキーワード: mixed alpha beta, proton transfer, cytosolic, lyase
• 由来する生物種: Homo sapiens (human)
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 29354.47

構造登録者

Fisher, S.Z.,McKenna, R. (登録日: 2014-04-14, 公開日: 2015-02-25, 最終更新日: 2023-09-20)

主引用文献

Michalczyk, R.,Unkefer, C.J.,Bacik, J.P.,Schrader, T.E.,Ostermann, A.,Kovalevsky, A.Y.,McKenna, R.,Fisher, S.Z.
Joint neutron crystallographic and NMR solution studies of Tyr residue ionization and hydrogen bonding: Implications for enzyme-mediated proton transfer.
Proc.Natl.Acad.Sci.USA, 112:5673-5678, 2015

PubMed Abstract: Human carbonic anhydrase II (HCA II) uses a Zn-bound OH(-)/H2O mechanism to catalyze the reversible hydration of CO2. This catalysis also involves a separate proton transfer step, mediated by an ordered solvent network coordinated by hydrophilic residues. One of these residues, Tyr7, was previously shown to be deprotonated in the neutron crystal structure at pH 10. This observation indicated that Tyr7 has a perturbed pKa compared with free tyrosine. To further probe the pKa of this residue, NMR spectroscopic measurements of [(13)C]Tyr-labeled holo HCA II (with active-site Zn present) were preformed to titrate all Tyr residues between pH 5.4-11.0. In addition, neutron studies of apo HCA II (with Zn removed from the active site) at pH 7.5 and holo HCA II at pH 6 were conducted. This detailed interrogation of tyrosines in HCA II by NMR and neutron crystallography revealed a significantly lowered pKa of Tyr7 and how pH and Tyr proximity to Zn affect hydrogen-bonding interactions.

PubMed: 25902526
DOI: 10.1073/pnas.1502255112

実験手法

NEUTRON DIFFRACTION (1.8 Å)