1LZV

Site-Specific Mutant (Tyr7 replaced with His) of Human Carbonic Anhydrase II

Summary for 1LZV

• Entry DOI: 10.2210/pdb1lzv/pdb
• Descriptor: Carbonic Anhydrase II, ZINC ION (3 entities in total)
• Functional Keywords: twisted beta sheet, zinc metalloenzyme, lyase
• Biological source: Homo sapiens (human)
• Cellular location: Cytoplasm: P00918
• Total number of polymer chains: 1
• Total formula weight: 29329.44

Authors

Tu, C.K.,Qian, M.,An, H.,Wadhwa, N.R.,Duda, D.M.,Yoshioka, C.,Pathak, Y.,McKenna, R.,Laipis, P.J.,Silverman, D.N. (deposition date: 2002-06-11, release date: 2002-10-23, Last modification date: 2024-02-14)

Primary citation

Tu, C.,Qian, M.,An, H.,Wadhwa, N.R.,Duda, D.,Yoshioka, C.,Pathak, Y.,McKenna, R.,Laipis, P.J.,Silverman, D.N.
Kinetic analysis of multiple proton shuttles in the active site of human carbonic anhydrase.
J.Biol.Chem., 277:38870-38876, 2002

PubMed Abstract: We have prepared a site-specific mutant of human carbonic anhydrase (HCA) II with histidine residues at positions 7 and 64 in the active site cavity. Using a different isozyme, we have placed histidine residues in HCA III at positions 64 and 67 and in another mutant at positions 64 and 7. Each of these histidine residues can act as a proton transfer group in catalysis when it is the only nonliganding histidine in the active site cavity, except His(7) in HCA III. Using an (18)O exchange method to measure rate constants for intramolecular proton transfer, we have found that inserting two histidine residues into the active site cavity of either isozyme II or III of carbonic anhydrase results in rates of proton transfer to the zinc-bound hydroxide that are antagonistic or suppressive with respect to the corresponding single mutants. The crystal structure of Y7H HCA II, which contains both His(7) and His(64) within the active site cavity, shows the conformation of the side chain of His(64) moved from its position in the wild type and hydrogen-bonded through an intervening water molecule with the side chain of His(7). This suggests a cause of decreased proton transfer in catalysis.

PubMed: 12171926
DOI: 10.1074/jbc.M205791200

Experimental method

X-RAY DIFFRACTION (2.3 Å)