1LG6

Crystal Structure Analysis of HCA II Mutant T199P in Complex with Thiocyanate

Summary for 1LG6

• Entry DOI: 10.2210/pdb1lg6/pdb
• Related: 1LG5 1LGD
• Descriptor: Carbonic anhydrase II, ZINC ION, THIOCYANATE ION, ... (4 entities in total)
• Functional Keywords: hcaii mutant t199p-scn complex, lyase
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm: P00918
• Total number of polymer chains: 1
• Total formula weight: 29392.50

Authors

Huang, S.,Sjoblom, B.,Sauer-Eriksson, A.E.,Jonsson, B.-H. (deposition date: 2002-04-15, release date: 2002-07-24, Last modification date: 2024-02-14)

Primary citation

Huang, S.,Sjoblom, B.,Sauer-Eriksson, A.E.,Jonsson, B.H.
Organization of an efficient carbonic anhydrase: implications for the mechanism based on structure-function studies of a T199P/C206S mutant.
Biochemistry, 41:7628-7635, 2002

PubMed Abstract: Substitution of Pro for Thr199 in the active site of human carbonic anhydrase II (HCA II)(1) reduces its catalytic efficiency about 3000-fold. X-ray crystallographic structures of the T199P/C206S variant have been determined in complex with the substrate bicarbonate and with the inhibitors thiocyanate and beta-mercaptoethanol. The latter molecule is normally not an inhibitor of wild-type HCA II. All three ligands display novel binding interactions to the T199P/C206S mutant. The beta-mercaptoethanol molecule binds in the active site area with its sulfur atom tetrahedrally coordinated to the zinc ion. Thiocyanate binds tetrahedrally coordinated to the zinc ion in T199P/C206S, in contrast to its pentacoordinated binding to the zinc ion in wild-type HCA II. Bicarbonate binds to the mutant with two of its oxygens at the positions of the zinc water (Wat263) and Wat318 in wild-type HCA II. The environment of this area is more hydrophilic than the normal bicarbonate-binding site of HCA II situated in the hydrophobic part of the cavity normally occupied by the so-called deep water (Wat338). The observation of a new binding site for bicarbonate has implications for understanding the mechanism by which the main-chain amino group of Thr199 acquired an important role for orientation of the substrate during the evolution of the enzyme.

PubMed: 12056894
DOI: 10.1021/bi020053o

Experimental method

X-RAY DIFFRACTION (2.2 Å)