Structural and biochemical studies of plant inositol phosphate kinases
type: CreativeWork
description: Among inositol phosphates, inositol hexakisphosphate constitutes the main form of phosphorus storage in seeds and beans. However, the pathway(s) of inositol hexakisphosphatesynthesis, particularly in plants, remain incomplete. To further our understanding of these pathways, five inositol phosphate kinases: AtIPK1, AtITPK2, AtITPK4, StIPMK and StIPKα, along with two inositol Phosphate binding proteins: COI1 and TIR1, were cloned with the aim of fully characterising each. The research became centered around AtIPK1, although AtITPK4 was also investigated as a novel ITPK family member. X-ray crystallographic structures of AtIPK1XHis in complex with myo-inositol hexakisphosphate, myo-inositol 1,3,4,5,6-pentakisphosphate, neo- and D-chiro-inositol pentakisphosphate were collected to aid understanding of substrate use. Structural data showed that AtIPK1 was able to form a complex with these substrates. Enzyme assays revealed that neo-inositol 1,3,4,6-tetrakisphosphate and D-chiro-inositol 2,3,4,5-tetrakisphosphate are phosphorylated twice by AtIPK1, producing neo-inositol hexakisphosphate and D-chiro-inositol hexakisphosphate. The enzyme was shown to catalyze phosphotransfer reactions in the reverse direction. The reactions shown to be catalyzed by AtIPK1 afford potential explanation of the range of inositol phosphate Stereoisomers found in soils. Solved crystal structures of binary and ternary complexes of AtIPK1, nucleotide and individual benzene tetrakisphosphates, a group of novel compounds which have been proposed as structural mimics of inositol phosphates, revealed that AtIPK1 binds these inositol phosphate mimics. Complementary enzyme assays showed no evidence of addition or removal of phosphates from these mimics. Further assays demonstrated that benzene phosphates are inhibitors of AtIPK1, offering potential for the design of stronger inhibitors of this enzyme. AtIPK1 contains a zinc ion coordinated by a zinc finger motif that is conserved in all plant IPK1 homol…
abstract: Among inositol phosphates, inositol hexakisphosphate constitutes the main form of phosphorus storage in seeds and beans. However, the pathway(s) of inositol hexakisphosphatesynthesis, particularly in plants, remain incomplete. To further our understanding of these pathways, five inositol phosphate kinases: AtIPK1, AtITPK2, AtITPK4, StIPMK and StIPKα, along with two inositol Phosphate binding proteins: COI1 and TIR1, were cloned with the aim of fully characterising each. The research became centered around AtIPK1, although AtITPK4 was also investigated as a novel ITPK family member. X-ray crystallographic structures of AtIPK1XHis in complex with myo-inositol hexakisphosphate, myo-inositol 1,3,4,5,6-pentakisphosphate, neo- and D-chiro-inositol pentakisphosphate were collected to aid understanding of substrate use. Structural data showed that AtIPK1 was able to form a complex with these substrates. Enzyme assays revealed that neo-inositol 1,3,4,6-tetrakisphosphate and D-chiro-inositol 2,3,4,5-tetrakisphosphate are phosphorylated twice by AtIPK1, producing neo-inositol hexakisphosphate and D-chiro-inositol hexakisphosphate. The enzyme was shown to catalyze phosphotransfer reactions in the reverse direction. The reactions shown to be catalyzed by AtIPK1 afford potential explanation of the range of inositol phosphate Stereoisomers found in soils. Solved crystal structures of binary and ternary complexes of AtIPK1, nucleotide and individual benzene tetrakisphosphates, a group of novel compounds which have been proposed as structural mimics of inositol phosphates, revealed that AtIPK1 binds these inositol phosphate mimics. Complementary enzyme assays showed no evidence of addition or removal of phosphates from these mimics. Further assays demonstrated that benzene phosphates are inhibitors of AtIPK1, offering potential for the design of stronger inhibitors of this enzyme. AtIPK1 contains a zinc ion coordinated by a zinc finger motif that is conserved in all plant IPK1 homol…
author: Whitfield, Hayley
language: en
date published: 2013-09
date modified: 2026-07-24T02:11:59Z
provider: University of East Anglia
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of East Anglia