1H4N

H94N CARBONIC ANHYDRASE II COMPLEXED WITH TRIS


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.154 
  • R-Value Observed: 0.154 

wwPDB Validation   3D Report Full Report


This is version 1.3 of the entry. See complete history


Literature

Histidine --> carboxamide ligand substitutions in the zinc binding site of carbonic anhydrase II alter metal coordination geometry but retain catalytic activity.

Lesburg, C.A.Huang, C.Christianson, D.W.Fierke, C.A.

(1997) Biochemistry 36: 15780-15791

  • DOI: 10.1021/bi971296x
  • Primary Citation of Related Structures:  
    1H4N, 1H9N, 1H9Q, 2H4N

  • PubMed Abstract: 
  • 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 ...

    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.


    Organizational Affiliation

    Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
CARBONIC ANHYDRASE IIA259Homo sapiensMutation(s): 1 
Gene Names: CAIICA2
EC: 4.2.1.1
UniProt & NIH Common Fund Data Resources
Find proteins for P00918 (Homo sapiens)
Explore P00918 
Go to UniProtKB:  P00918
PHAROS:  P00918
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
TRS
Query on TRS

Download Ideal Coordinates CCD File 
C [auth A]2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL
C4 H12 N O3
LENZDBCJOHFCAS-UHFFFAOYSA-O
 Ligand Interaction
ZN
Query on ZN

Download Ideal Coordinates CCD File 
B [auth A]ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
 Ligand Interaction
Binding Affinity Annotations 
IDSourceBinding Affinity
TRS PDBBind:  1H4N Ki: 1.20e+4 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Free: 0.207 
  • R-Value Work: 0.154 
  • R-Value Observed: 0.154 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 42.7α = 90
b = 41.7β = 104.6
c = 73γ = 90
Software Package:
Software NamePurpose
X-PLORmodel building
X-PLORrefinement
MOSFLMdata reduction
CCP4data scaling
X-PLORphasing

Structure Validation

View Full Validation Report




Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1997-09-17
    Type: Initial release
  • Version 1.1: 2008-03-24
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2021-11-03
    Changes: Database references, Derived calculations, Other