title: Regulation of hexokinase I: crystal structure of recombinant human brain hexokinase complexed with glucose and phosphate.
abstract: Hexokinase I, the pacemaker of glycolysis in brain tissue and red blood cells, is comprised of two similar domains fused into a single polypeptide chain. The C-terminal half of hexokinase I is catalytically active, whereas the N-terminal half is necessary for the relief of product inhibition by phosphate. A crystalline complex of recombinant human hexokinase I with glucose and phosphate (2.8 A resolution) reveals a single binding site for phosphate and glucose at the N-terminal half of the enzyme. Glucose and phosphate stabilize the N-terminal half in a closed conformation. Unexpectedly, glucose binds weakly to the C-terminal half of the enzyme and does not by itself stabilize a closed conformation. Evidently a stable, closed C-terminal half requires either ATP or glucose 6-phosphate along with glucose. The crystal structure here, in conjunction with other studies in crystallography and directed mutation, puts the phosphate regulatory site at the N-terminal half, the site of potent product inhibition at the C-terminal half, and a secondary site for the weak interaction of glucose 6-phosphate at the N-terminal half of the enzyme. The relevance of crystal structures of hexokinase I to the properties of monomeric hexokinase I and oligomers of hexokinase I bound to the surface of mitochondria is discussed.
authors.affiliation: Department of Biochemistry and Biophysics, Iowa State University, Ames, IA 50011, USA.
authors.forename: A E
authors.initials: AE
authors.lastname: Aleshin
authors.forename: C
authors.initials: C
authors.lastname: Zeng
authors.forename: H D
authors.initials: HD
authors.lastname: Bartunik
authors.forename: H J
authors.initials: HJ
authors.lastname: Fromm
authors.forename: R B
authors.initials: RB
authors.lastname: Honzatko
mesh_terms: D001921:Brain / Q000201:enzymology*; D018360:Crystallography, X-Ray; D019281:Dimerization; D005947:Glucose / Q000737:chemistry*; D006593:Hexokinase / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008024:Ligands; D010710:Phosphates; D011994:Recombinant Proteins; D006593:Hexokinase; D005947:Glucose