5CA2

CONFORMATIONAL MOBILITY OF HIS-64 IN THE THR-200 (RIGHT ARROW) SER MUTANT OF HUMAN CARBONIC ANHYDRASE II

Summary for 5CA2

• Entry DOI: 10.2210/pdb5ca2/pdb
• Descriptor: CARBONIC ANHYDRASE II, ZINC ION, MERCURY (II) ION, ... (4 entities in total)
• Functional Keywords: lyase(oxo-acid)
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm : P00918
• Total number of polymer chains: 1
• Total formula weight: 29541.03

Authors

Alexander, R.S.,Christianson, D.W. (deposition date: 1991-06-08, release date: 1992-10-31, Last modification date: 2024-03-06)

Primary citation

Krebs, J.F.,Fierke, C.A.,Alexander, R.S.,Christianson, D.W.
Conformational mobility of His-64 in the Thr-200----Ser mutant of human carbonic anhydrase II.
Biochemistry, 30:9153-9160, 1991

PubMed 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.

PubMed: 1909891
DOI: 10.1021/bi00102a005

Experimental method

X-RAY DIFFRACTION (2.1 Å)