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Structures of alternatively spliced isoforms of human ketohexokinase.

Trinh CH, Asipu A, Bonthron DT, Phillips SE - Acta Crystallogr. D Biol. Crystallogr. (2009)

Bottom Line: The structure of the KHK-A ternary complex revealed an active site with both the substrate fructose and the ATP analogue in positions ready for phosphorylation following a reaction mechanism similar to that of the pfkB family of carbohydrate kinases.Hepatic KHK deficiency causes the benign disorder essential fructosuria.The effects of the disease-causing mutations (Gly40Arg and Ala43Thr) have been modelled in the context of the KHK structure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, University of Leeds, Leeds, England.

ABSTRACT
A molecular understanding of the unique aspects of dietary fructose metabolism may be the key to understanding and controlling the current epidemic of fructose-related obesity, diabetes and related adverse metabolic states in Western populations. Fructose catabolism is initiated by its phosphorylation to fructose 1-phosphate, which is performed by ketohexokinase (KHK). Here, the crystal structures of the two alternatively spliced isoforms of human ketohexokinase, hepatic KHK-C and the peripheral isoform KHK-A, and of the ternary complex of KHK-A with the substrate fructose and AMP-PNP are reported. The structure of the KHK-A ternary complex revealed an active site with both the substrate fructose and the ATP analogue in positions ready for phosphorylation following a reaction mechanism similar to that of the pfkB family of carbohydrate kinases. Hepatic KHK deficiency causes the benign disorder essential fructosuria. The effects of the disease-causing mutations (Gly40Arg and Ala43Thr) have been modelled in the context of the KHK structure.

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Structure of human KHK-A. (a) A topology diagram of the human ketohexokinase subunit. The α-helices are shown as cylinders and the β-­strands as arrows. Each secondary-structural element is labelled with its starting and ending sequence number. The secondary-structural elements were defined using DSSP (Kabsch & Sander, 1983 ▶). (b) A ribbon diagram representing the overall fold of the KHK subunit. The core domain of the monomer is comprised of a nine-stranded β-sheet flanked on both sides by α-helices. The four-stranded β-sheet formed by β2, β6, β7 (cyan) and β3 (yellow) extends away from the core domain, leaving a cleft for the active site. β3 is separated into two strands, β3a and β3b, by a bend at residues 32–33 that lies at the C-terminal end of β-strand β3a.
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fig2: Structure of human KHK-A. (a) A topology diagram of the human ketohexokinase subunit. The α-helices are shown as cylinders and the β-­strands as arrows. Each secondary-structural element is labelled with its starting and ending sequence number. The secondary-structural elements were defined using DSSP (Kabsch & Sander, 1983 ▶). (b) A ribbon diagram representing the overall fold of the KHK subunit. The core domain of the monomer is comprised of a nine-stranded β-sheet flanked on both sides by α-helices. The four-stranded β-sheet formed by β2, β6, β7 (cyan) and β3 (yellow) extends away from the core domain, leaving a cleft for the active site. β3 is separated into two strands, β3a and β3b, by a bend at residues 32–33 that lies at the C-terminal end of β-strand β3a.

Mentions: The KHK-A subunit has two distinct domains: a central α/β-fold and a four-stranded β-sheet. The α/β-fold consists of a nine-stranded β-sheet flanked on each side by five α-helices: α1, α2, α8, α9, α10 and α3, α4, α5, α6, α7 (Fig. 2 ▶). The overall structures of KHK-A and of its binary and ternary complexes are very similar, with no significant differences in main-chain conformation, except for a small region between residues 113 and 116 (Tyr113, Asp114, Arg115 and Ser116). The electron density around residues 115 and 116 is weaker, suggesting some flexibility, and alternative main-chain conformations may exist.


Structures of alternatively spliced isoforms of human ketohexokinase.

Trinh CH, Asipu A, Bonthron DT, Phillips SE - Acta Crystallogr. D Biol. Crystallogr. (2009)

Structure of human KHK-A. (a) A topology diagram of the human ketohexokinase subunit. The α-helices are shown as cylinders and the β-­strands as arrows. Each secondary-structural element is labelled with its starting and ending sequence number. The secondary-structural elements were defined using DSSP (Kabsch & Sander, 1983 ▶). (b) A ribbon diagram representing the overall fold of the KHK subunit. The core domain of the monomer is comprised of a nine-stranded β-sheet flanked on both sides by α-helices. The four-stranded β-sheet formed by β2, β6, β7 (cyan) and β3 (yellow) extends away from the core domain, leaving a cleft for the active site. β3 is separated into two strands, β3a and β3b, by a bend at residues 32–33 that lies at the C-terminal end of β-strand β3a.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2651755&req=5

fig2: Structure of human KHK-A. (a) A topology diagram of the human ketohexokinase subunit. The α-helices are shown as cylinders and the β-­strands as arrows. Each secondary-structural element is labelled with its starting and ending sequence number. The secondary-structural elements were defined using DSSP (Kabsch & Sander, 1983 ▶). (b) A ribbon diagram representing the overall fold of the KHK subunit. The core domain of the monomer is comprised of a nine-stranded β-sheet flanked on both sides by α-helices. The four-stranded β-sheet formed by β2, β6, β7 (cyan) and β3 (yellow) extends away from the core domain, leaving a cleft for the active site. β3 is separated into two strands, β3a and β3b, by a bend at residues 32–33 that lies at the C-terminal end of β-strand β3a.
Mentions: The KHK-A subunit has two distinct domains: a central α/β-fold and a four-stranded β-sheet. The α/β-fold consists of a nine-stranded β-sheet flanked on each side by five α-helices: α1, α2, α8, α9, α10 and α3, α4, α5, α6, α7 (Fig. 2 ▶). The overall structures of KHK-A and of its binary and ternary complexes are very similar, with no significant differences in main-chain conformation, except for a small region between residues 113 and 116 (Tyr113, Asp114, Arg115 and Ser116). The electron density around residues 115 and 116 is weaker, suggesting some flexibility, and alternative main-chain conformations may exist.

Bottom Line: The structure of the KHK-A ternary complex revealed an active site with both the substrate fructose and the ATP analogue in positions ready for phosphorylation following a reaction mechanism similar to that of the pfkB family of carbohydrate kinases.Hepatic KHK deficiency causes the benign disorder essential fructosuria.The effects of the disease-causing mutations (Gly40Arg and Ala43Thr) have been modelled in the context of the KHK structure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, University of Leeds, Leeds, England.

ABSTRACT
A molecular understanding of the unique aspects of dietary fructose metabolism may be the key to understanding and controlling the current epidemic of fructose-related obesity, diabetes and related adverse metabolic states in Western populations. Fructose catabolism is initiated by its phosphorylation to fructose 1-phosphate, which is performed by ketohexokinase (KHK). Here, the crystal structures of the two alternatively spliced isoforms of human ketohexokinase, hepatic KHK-C and the peripheral isoform KHK-A, and of the ternary complex of KHK-A with the substrate fructose and AMP-PNP are reported. The structure of the KHK-A ternary complex revealed an active site with both the substrate fructose and the ATP analogue in positions ready for phosphorylation following a reaction mechanism similar to that of the pfkB family of carbohydrate kinases. Hepatic KHK deficiency causes the benign disorder essential fructosuria. The effects of the disease-causing mutations (Gly40Arg and Ala43Thr) have been modelled in the context of the KHK structure.

Show MeSH
Related in: MedlinePlus