|1cza, resolution 1.90Å ()|
MUTANT MONOMER OF RECOMBINANT HUMAN HEXOKINASE TYPE I COMPLEXED WITH GLUCOSE, GLUCOSE-6-PHOSPHATE, AND ADP
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.
Crystal structures of mutant monomeric hexokinase I reveal multiple ADP binding sites and conformational changes relevant to allosteric regulation., Aleshin AE, Kirby C, Liu X, Bourenkov GP, Bartunik HD, Fromm HJ, Honzatko RB, J Mol Biol. 2000 Mar 3;296(4):1001-15. PMID:10686099
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
[HXK1_HUMAN] Defects in HK1 are the cause of hexokinase deficiency (HK deficiency) [MIM:235700]. HK deficiency is a rare autosomal recessive disease with nonspherocytic hemolytic anemia as the predominant clinical feature.
About this Structure
- Aleshin AE, Kirby C, Liu X, Bourenkov GP, Bartunik HD, Fromm HJ, Honzatko RB. 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. PMID:10686099 doi:10.1006/jmbi.1999.3494