Crystal structures of mutant monomeric hexokinase I reveal multiple ADP binding sites and conformational changes relevant to allosteric regulation

J Mol Biol. 2000 Mar 3;296(4):1001-15. doi: 10.1006/jmbi.1999.3494.


Hexokinase I, the pacemaker of glycolysis in brain tissue, is composed of two structurally similar halves connected by an alpha-helix. The enzyme dimerizes at elevated protein concentrations in solution and in crystal structures; however, almost all published data reflect the properties of a hexokinase I monomer in solution. Crystal structures of mutant forms of recombinant human hexokinase I, presented here, reveal the enzyme monomer for the first time. The mutant hexokinases bind both glucose 6-phosphate and glucose with high affinity to their N and C-terminal halves, and ADP, also with high affinity, to a site near the N terminus of the polypeptide chain. Exposure of the monomer crystals to ADP in the complete absence of glucose 6-phosphate reveals a second binding site for adenine nucleotides at the putative active site (C-half), with conformational changes extending 15 A to the contact interface between the N and C-halves. The structures reveal distinct conformational states for the C-half and a rigid-body rotation of the N-half, as possible elements of a structure-based mechanism for allosteric regulation of catalysis.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Diphosphate / chemistry
  • Adenosine Diphosphate / metabolism*
  • Allosteric Regulation
  • Binding Sites
  • Crystallography, X-Ray
  • Escherichia coli / enzymology
  • Glucose-6-Phosphate / chemistry
  • Glucose-6-Phosphate / metabolism
  • Hexokinase / chemistry*
  • Hexokinase / metabolism
  • Models, Molecular
  • Protein Conformation


  • Glucose-6-Phosphate
  • Adenosine Diphosphate
  • Hexokinase

Associated data

  • PDB/1CZA
  • PDB/1DGK