Article Metrics


Online attention

Diversification in the inositol tris/tetrakisphosphate kinase (ITPK) family: crystal structure and enzymology of the outlier AtITPK4

DOI: 10.1042/BCJ20220579 DOI Help

Authors: Hayley Whitfield (University of East Anglia) , Sining He (University of East Anglia) , Yinghong Gu (University of East Anglia) , Colleen Sprigg (University of East Anglia) , Hui-Fen Kuo (Academia Sinica) , Tzyy-Jen Chiou (Academia Sinica) , Andrew M. Riley (University of Oxford) , Barry V. L. Potter (University of Oxford) , Andrew M. Hemmings (University of East Anglia) , Charles A. Brearley (University of East Anglia)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: March 2023
Diamond Proposal Number(s): 18565

Open Access Open Access

Abstract: Myo-inositol tris/tetrakisphosphate kinases (ITPKs) catalyze diverse phosphotransfer reactions with myo-inositol phosphate and myo-inositol pyrophosphate substrates. However, the lack of structures of nucleotide-coordinated plant ITPKs thwarts a rational understanding of phosphotransfer reactions of the family. Arabidopsis possesses a family of four ITPKs of which two isoforms, ITPK1 and ITPK4, control inositol hexakisphosphate and inositol pyrophosphate levels directly or by provision of precursors. Here, we describe the specificity of Arabidopsis ITPK4 to pairs of enantiomers of diverse inositol polyphosphates and show how substrate specificity differs from Arabidopsis ITPK1. Moreover, we provide a description of the crystal structure of ATP-coordinated AtITPK4 at 2.11 Å resolution that along with description of the enantiospecificity of the enzyme affords a molecular explanation for the diverse phosphotransferase activity of this enzyme. That Arabidopsis ITPK4 has a Km for ATP in the tens of micromolar range, potentially explains how, despite the large-scale abolition of InsP6, InsP7 and InsP8 synthesis in Atitpk4 mutants, Atitpk4 lacks the phosphate starvation responses of Atitpk1 mutants. We further demonstrate that Arabidopsis ITPK4 and its homologs in other plants possess an N-terminal haloacid dehalogenase-like fold not previously described. The structural and enzymological information revealed will guide elucidation of ITPK4 function in diverse physiological contexts, including InsP8-dependent aspects of plant biology.

Journal Keywords: ATP Grasp; HAD domain; inositol polyphosphates

Diamond Keywords: Enzymes

Subject Areas: Biology and Bio-materials

Instruments: I04-Macromolecular Crystallography

Added On: 14/03/2023 10:34

Discipline Tags:

Plant science Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)