Diversification in the inositol tris/tetrakisphosphate kinase (ITPK) family: crystal structure and enzymology of the outlier AtITPK4.
Diversification in the inositol tris/tetrakisphosphate kinase (ITPK) family: crystal structure and enzymology of the outlier AtITPK4.
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DOI：
10.1042/bcj20220579
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发表时间：
2023-03-29
期刊：
影响因子：
--
通讯作者：
Brearley CA
中科院分区：
文献类型：
--
作者：
Whitfield HL;He S;Gu Y;Sprigg C;Kuo HF;Chiou TJ;Riley AM;Potter BVL;Hemmings AM;Brearley CA
肌醇三/四磷酸激酶（ITPKs）催化肌醇磷酸和肌醇焦磷酸底物的多种磷酸转移反应。然而，缺乏结构的核苷酸协调的植物ITPKs阻碍了合理理解的磷酸转移反应的家庭。拟南芥具有四个ITPK家族，其中两个亚型ITPK 1和ITPK 4直接或通过提供前体来控制肌醇六磷酸和肌醇焦磷酸水平。在这里，我们描述了拟南芥ITPK 4的特异性对不同的肌醇多磷酸对映异构体，并显示如何从拟南芥ITPK 1底物特异性不同。此外，我们提供了一个描述的晶体结构的ATP-协调的AtITPK 4在2.11沿着的酶的对映体特异性的描述，提供了一个分子的解释不同的磷酸转移酶活性的这种酶。 拟南芥ITPK 4对ATP的KM在几十微摩尔范围内，这可能解释了尽管Atitpk 4突变体中InsP 6、InsP 7和InsP 8合成大规模取消，但Atitpk 4缺乏Atitpk 1突变体的磷酸饥饿反应。我们进一步证明，拟南芥ITPK 4和它的同源物在其他植物中具有N-末端卤酸脱卤酶样折叠以前没有描述过。揭示的结构和酶学信息将指导阐明ITPK 4在不同生理环境中的功能，包括InsP 8依赖的植物生物学方面。
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.
拟南芥 VSP1 的晶体结构揭示了磷酸水解酶 DDDD 超家族的植物 C 类磷酸酶结构
影响因子：
3.7
作者：
Chen Y;Wei J;Wang M;Shi Z;Gong W;Zhang M
通讯作者：
Zhang M