PMID- 9398308
OWN - NLM
STAT- MEDLINE
DCOM- 19980127
LR  - 20131121
IS  - 0006-2960 (Print)
IS  - 0006-2960 (Linking)
VI  - 36
IP  - 50
DP  - 1997 Dec 16
TI  - Histidine --> carboxamide ligand substitutions in the zinc binding site of 
      carbonic anhydrase II alter metal coordination geometry but retain catalytic 
      activity.
PG  - 15780-91
AB  - The catalytic zinc ion of human carbonic anhydrase II (CAII) is coordinated by 
      three histidine ligands (H94, H96, and H119) and a hydroxide ion with tetrahedral 
      geometry. Structural and functional analysis of variants in which the zinc 
      ligands H94 and H119 are substituted with asparagine and glutamine, and 
      comparison with results obtained with aspartate and glutamate substitutions 
      indicate that the neutral ligand field provided by the protein optimizes the 
      electrostatic environment for the catalytic function of the metal ion, including 
      stabilization of bound anions. This is demonstrated by catalytic activity 
      measurements for ester hydrolysis and CO2 hydration, as well as sulfonamide 
      inhibitor affinity assays. High-resolution X-ray crystal structure determinations 
      of H94N, H119N, and H119Q CAIIs reveal that the engineered carboxamide side 
      chains coordinate to zinc with optimal stereochemistry. However, zinc 
      coordination geometry remains tetrahedral only in H119Q CAII. Metal geometry 
      changes to trigonal bipyramidal in H119N CAII due to the addition of a second 
      water molecule to the zinc coordination polyhedron and also in H94N CAII due to 
      the displacement of zinc-bound hydroxide by the bidentate coordination of a Tris 
      molecule. Possibly, the bulky histidine imidazole ligands of the native enzyme 
      play a role in disfavoring trigonal bipyramidal coordination geometry for zinc. 
      Protein-metal affinity is significantly compromised by all histidine --> 
      carboxamide ligand substitutions. Diminished affinity may result from significant 
      movements (up to 1 A) of the metal ion from its position in the wild-type enzyme, 
      as well as the associated, minor conformational changes of metal ligands and 
      their neighboring residues.
FAU - Lesburg, C A
AU  - Lesburg CA
AD  - Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 
      19104-6323, USA.
FAU - Huang, C
AU  - Huang C
FAU - Christianson, D W
AU  - Christianson DW
FAU - Fierke, C A
AU  - Fierke CA
LA  - eng
GR  - GM07229/GM/NIGMS NIH HHS/United States
GR  - GM40602/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Biochemistry
JT  - Biochemistry
JID - 0370623
RN  - 0 (Enzyme Inhibitors)
RN  - 0 (Ligands)
RN  - 0 (Nitrophenols)
RN  - 0 (Sulfonamides)
RN  - 142M471B3J (Carbon Dioxide)
RN  - 4QD397987E (Histidine)
RN  - 830-03-5 (4-nitrophenyl acetate)
RN  - EC 3.1.- (Esterases)
RN  - EC 4.2.1.1 (Carbonic Anhydrases)
RN  - J41CSQ7QDS (Zinc)
SB  - IM
MH  - Binding Sites
MH  - Carbon Dioxide/metabolism
MH  - Carbonic Anhydrases/chemistry/genetics/*metabolism
MH  - Catalysis
MH  - Crystallography, X-Ray
MH  - Enzyme Inhibitors/pharmacology
MH  - Esterases/metabolism
MH  - Histidine/metabolism
MH  - Humans
MH  - Hydrogen Bonding
MH  - Hydrogen-Ion Concentration
MH  - Kinetics
MH  - Ligands
MH  - Models, Molecular
MH  - Mutagenesis, Site-Directed
MH  - Nitrophenols/metabolism
MH  - Sulfonamides/pharmacology
MH  - Zinc/*metabolism
EDAT- 1998/01/31 00:00
MHDA- 1998/01/31 00:01
CRDT- 1998/01/31 00:00
PHST- 1998/01/31 00:00 [pubmed]
PHST- 1998/01/31 00:01 [medline]
PHST- 1998/01/31 00:00 [entrez]
AID - bi971296x [pii]
AID - 10.1021/bi971296x [doi]
PST - ppublish
SO  - Biochemistry. 1997 Dec 16;36(50):15780-91. doi: 10.1021/bi971296x.