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Crystallographic analysis of Thr‐200 → His human carbonic anhydrase II and its complex with the substrate, HCO 3 −
Author(s) -
Xue Yafeng,
Vidgren Jukka,
Svensson L. Anders,
Liljas Anders,
Jonsson BengtHarald,
Lindskog Sven
Publication year - 1993
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340150110
Subject(s) - chemistry , bicarbonate , carbonic anhydrase ii , carbonic anhydrase , zinc , trigonal bipyramidal molecular geometry , ligand (biochemistry) , crystallography , denticity , active site , hydroxide , histidine , stereochemistry , inorganic chemistry , catalysis , crystal structure , enzyme , biochemistry , receptor , organic chemistry
A complex of carbonic anhydrase (CA) with one of its substrates, bicarbonate, has been studied crystallographically. Human isoenzyme II was mutated at position 200 from threonine to histidine, which results in higher affinity for bicarbonate. The HCO 3 −ion binds in the active site to the zinc ion as a pseudo‐bidentate ligand which gives the metal a coordination geometry between tetrahedral and trigonal bipyramide. The water/hydroxide normally bound with tetrahedral coordination to the zinc is probably replaced by the OH group of the bicarbonate ion. The importance of residues Thr‐199 and Glu‐106 in controlling the binding orientation of HCO 3 −is discussed as well as the catalytic mechanism. Both the complex as well as the uncomplexed mutant were studied at 1.9 Å resolution. © 1993 Wiley‐Liss, Inc.