1HQA

ALKALINE PHOSPHATASE (H412Q)


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.25 Å
  • R-Value Work: 0.161 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Kinetic and X-ray structural studies of a mutant Escherichia coli alkaline phosphatase (His-412-->Gln) at one of the zinc binding sites.

Ma, L.Kantrowitz, E.R.

(1996) Biochemistry 35: 2394-2402

  • DOI: 10.1021/bi9523421

  • PubMed Abstract: 
  • Site-specific mutagenesis has been used to replace His-412 with glutamine in Escherichia coli alkaline phosphatase. In the wild-type enzyme His-412 is a direct ligand to one of the catalytically important zinc atoms (Zn1) in the active site. The muta ...

    Site-specific mutagenesis has been used to replace His-412 with glutamine in Escherichia coli alkaline phosphatase. In the wild-type enzyme His-412 is a direct ligand to one of the catalytically important zinc atoms (Zn1) in the active site. The mutant enzyme (H412Q) exhibited about the same k(cat), but a 50-fold increase in K(m) compared to the corresponding kinetic parameters for the wild-type enzyme. Furthermore, the H412Q enzyme had a lower zinc content than the wild-type enzyme. In contrast to the wild-type enzyme, Tris was less effective in the transferase reaction and dramatically inhibited the hydrolysis reaction of the H412Q enzyme. The addition of zinc to the mutant enzyme increased the k(cat) value above that of the wild-type enzyme, partially restored the weak substrate and phosphate binding, and also alleviated the inhibition by Tris. The structure of the H412Q enzyme was also determined by X-ray crystallography. The overall structure of the H412Q enzyme was very similar to that of the wild-type enzyme; the only alpha-carbon displacements over 1 angstrom were observed near the mutation site. In the H412Q structure no phosphate was bound in the active site of the enzyme; however, two water molecules were observed where phosphate normally binds in the wild-type enzyme. Close examination of the active site of the H412Q structure revealed structural changes in Ser-102 as well as at the mutation site. For example, the carbonyl oxygen of the side chain of Gln-412 rotated away from the position of His-412 in the wild-type structure, although too far away (3.2 angstroms) to coordinate to Zn1. Studies on the H412Q enzyme, and a comparison of the H412Q and H412N structures, suggest that the structure and electostatics of the imidazole ring of histidine are critical for its function as a zinc ligand in alkaline phosphatase.


    Related Citations: 
    • Escherichia Coli Alkaline Phosphatase: X-Ray Structural Studies of a Mutant Enzyme (His-412-->Asn) at One of the Catalytically Important Zinc Binding Sites
      Ma, L.,Tibbitts, T.T.,Kantrowitz, E.R.
      (1995) Protein Sci. 4: 1498
    • Mutations at Histidine 412 Alter Zinc Binding and Eliminate Transferase Activity in Escherichia Coli Alkaline Phosphatase
      Ma, L.,Kantrowitz, E.R.
      (1994) J.Mol.Biol. 269: 31614
    • Reaction Mechanism of Alkaline Phosphatase Based on Crystal Structures. Two Metal Ion Catalysis
      Kim, E.E.,Wyckoff, H.W.
      (1991) J.Mol.Biol. 218: 449


    Organizational Affiliation

    Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachussetts 02167, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
ALKALINE PHOSPHATASE
A, B
449Escherichia coli (strain K12)Mutation(s): 1 
Gene Names: phoA
EC: 3.1.3.1
Find proteins for P00634 (Escherichia coli (strain K12))
Go to UniProtKB:  P00634
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
ZN
Query on ZN

Download SDF File 
Download CCD File 
A, B
ZINC ION
Zn
PTFCDOFLOPIGGS-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.25 Å
  • R-Value Work: 0.161 
  • Space Group: I 2 2 2
Unit Cell:
Length (Å)Angle (°)
a = 194.900α = 90.00
b = 167.000β = 90.00
c = 76.800γ = 90.00
Software Package:
Software NamePurpose
X-PLORrefinement
AREAdata collection
X-PLORphasing
ADSCdata collection
X-PLORmodel building

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1996-03-08
    Type: Initial release
  • Version 1.1: 2008-03-03
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance