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

Whitfield, Hayley L., He, Sining, Gu, Yinghong, Sprigg, Colleen, Kuo, Hui-Fen, Chiou, Tzyy-Jen, Riley, Andrew M., Potter, Barry V. L., Hemmings, Andrew M. ORCID: https://orcid.org/0000-0003-3053-3134 and Brearley, Charles A. ORCID: https://orcid.org/0000-0001-6179-9109 (2023) Diversification in the inositol tris/tetrakisphosphate kinase (ITPK) family: crystal structure and enzymology of the outlier AtITPK4. Biochemical Journal, 480 (6). 433–453. ISSN 0264-6021

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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 a 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 homologues 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.

Item Type: Article
Additional Information: Funding: This work was funded by the BBSRC through IPA award BB/M022978/1. SH was funded by a UEA-Southern University of Science and Technology (SUSTech, Shenzhen, China) Doctoral Training Studentship. This work was funded in part by The Wellcome Trust. BVLP is a Wellcome Trust Senior Investigator (grant 101010).
Uncontrolled Keywords: atp grasp,had domain,inositol polyphosphates,biochemistry,molecular biology,cell biology ,/dk/atira/pure/subjectarea/asjc/1300/1303
Faculty \ School: Faculty of Science > School of Biological Sciences
Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Plant Sciences
Faculty of Science > Research Groups > Molecular Microbiology
Faculty of Science > Research Groups > Chemistry of Life Processes
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
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Depositing User: LivePure Connector
Date Deposited: 28 Mar 2023 09:30
Last Modified: 26 Oct 2023 02:17
URI: https://ueaeprints.uea.ac.uk/id/eprint/91695
DOI: 10.1042/BCJ20220579

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