A novel context for the 'MutT' module, a guardian of cell integrity, in a diphosphoinositol polyphosphate phosphohydrolase
A novel context for the 'MutT' module, a guardian of cell integrity, in a diphosphoinositol polyphosphate phosphohydrolase
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DOI：
10.1093/emboj/17.22.6599
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发表时间：
1998-11-16
期刊：
影响因子：
11.4
通讯作者：
Shears, SB
中科院分区：
文献类型：
--
作者：
Safrany, ST;Caffrey, JJ;Shears, SB
二磷酸肌醇五磷酸（PP-InsP（5）或“InsP（7 ′）”）和双二磷酸肌醇四磷酸（[PP]（2）-InsP（4）或“InsP（8 ′）”）是基于肌醇的细胞信号传导家族中最高度磷酸化的成员。我们纯化了一种大鼠肝脏二磷酸肌醇多磷酸磷酸水解酶（DIPP），该酶可从PP-InsP（5）（K-m = 340 nM）和[PP]（2）-InsP（4）（K-m = 34 nM）中的二磷酸基团中切割β-磷酸。肌醇六磷酸（InsP（6））不是底物，但它抑制[PP]（2）-InsP（4）和PP-InsP（5）的代谢（IC 50分别为0.2和3 μ M）。DIPP的微测序揭示了“MutT”结构域，其在其他竞争中通过使8-oxo-dGTP去磷酸化来保护细胞完整性，这导致AT至CG颠换突变。MutT结构域还代谢一些可能在信号转导中起作用的核苷磷酸。大鼠DIPP MutT结构域在新型重组人子宫DIPP中是保守的。将人DIPP cDNA的核苷酸序列与6号染色体进行比对;候选基因包含至少四个外显子。通过保守的谷氨酸残基的诱变证实了DIPP的催化活性依赖于其MutT结构域。DIPP的低分子量、Mg ~（2+）依赖性和对磷酸酐键的催化偏好性也是其他MutT型蛋白的特征。由于重叠底物特异性是这类蛋白的一个特征，我们的数据为将来研究高级肌醇磷酸盐提供了新的方向。
Diphosphoinositol pentakisphosphate (PP-InsP(5) or 'InsP(7)') and bisdiphosphoinositol tetrakisphosphate ([PP](2)-InsP(4) or 'InsP(8)') are the most highly phosphorylated members of the inositol-based cell signaling family. We have purified a rat hepatic diphosphoinositol polyphosphate phosphohydrolase (DIPP) that cleaves a beta-phosphate from the diphosphate groups in PP-InsP(5) (K-m = 340 nM) and [PP](2)-InsP(4) (K-m = 34 nM). Inositol hexakisphophate (InsP(6)) was not a substrate, but it inhibited metabolism of both [PP](2)-InsP(4) and PP-InsP(5) (IC50 = 0.2 and 3 mu M, respectively). Microsequencing of DIPP revealed a 'MutT' domain, which in other contests guards cellular integrity by dephosphorylating 8-oxo-dGTP, which causes AT to CG transversion mutations. The MutT domain also metabolizes some nucleoside phosphates that may play roles in signal transduction. The rat DIPP MutT domain is conserved in a novel recombinant human uterine DIPP. The nucleotide sequence of the human DIPP cDNA was aligned to chromosome 6; the candidate gene contains at least four exons. The dependence of DIPP's catalytic activity upon its MutT domain was confirmed by mutagenesis of a conserved glutamate residue. DIPP's low molecular size, Mg2+ dependency and catalytic preference for phosphoanhydride bonds are also features of other MutT-type proteins, Because overlapping substrate specificity is a feature of this class of proteins, our data provide new directions for future studies of higher inositol phosphates.