PDBsum entry 5ca2

Lyase(oxo-acid)

PDB id: 5ca2

Contents

Protein chain

255 a.a. *

Metals

_HG

_ZN

Waters ×119

* Residue conservation analysis

PDB id:

5ca2

Name:

Lyase(oxo-acid)

Title:

Conformational mobility of his-64 in the thr-200 (right arrow) ser mutant of human carbonic anhydrase ii

Structure:

Carbonic anhydrase ii. Chain: a. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606

Resolution:

2.10Å R-factor: 0.160

Authors:

R.S.Alexander,D.W.Christianson

Key ref:

J.F.Krebs et al. (1991). Conformational mobility of His-64 in the Thr-200----Ser mutant of human carbonic anhydrase II. Biochemistry, 30, 9153-9160. PubMed id: 1909891 DOI: 10.1021/bi00102a005

Date:

08-Jun-91 Release date: 31-Oct-92

Protein chain

P00918  (CAH2_HUMAN) -  Carbonic anhydrase 2 from Homo sapiens

Seq: 260 a.a.

Struc: 255 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class 2: E.C.4.2.1.1 - carbonic anhydrase.
• Reaction: hydrogencarbonate + H⁺ = CO2 + H2O
• Cofactor: Zn(2+)
• Enzyme class 3: E.C.4.2.1.69 - cyanamide hydratase.
• Reaction: urea = cyanamide + H2O

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

DOI no: 10.1021/bi00102a005

Biochemistry 30:9153-9160 (1991)

PubMed id: 1909891

Conformational mobility of His-64 in the Thr-200----Ser mutant of human carbonic anhydrase II.

J.F.Krebs, C.A.Fierke, R.S.Alexander, D.W.Christianson.

ABSTRACT

The three-dimensional structure of the Thr-200----Ser (T200S) mutant of human carbonic anhydrase II (CAII) has been determined by X-ray crystallographic methods at 2.1-A resolution. This particular mutant of CAII exhibits CO2 hydrase activity that is comparable to that of the wild-type enzyme with a 2-fold stabilization of the E.HCO3- complex and esterase activity that is 4-fold greater than that of the wild-type enzyme. The structure of the mutant enzyme reveals no significant local changes accompanying the conservative T200S substitution, but an important nonlocal structural change is evident: the side chain of catalytic residue His-64 rotates away from the active site by 105 degrees about chi 1 and apparently displaces a water molecule. The displaced water molecule is present in the wild-type enzyme; however, the electron density into which this water is built is interpretable as an alternate conformation of His-64 with 10-20% occupancy. The rate constants for proton transfer from the zinc-water ligand to His-64 and from His-64 to bulk solvent are maintained in the T200S variant; therefore, if His-64 is conformationally mobile about chi 1 and/or chi 2 during catalysis, compensatory changes in solvent configuration must sustain efficient proton transfer.