New insights into the catalytic mechanism of histidine phosphatases revealed by a functionally essential arginine residue within the active site of the Sts phosphatases.
New insights into the catalytic mechanism of histidine phosphatases revealed by a functionally essential arginine residue within the active site of the Sts phosphatases.
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Sts 磷酸酶活性位点内功能必需的精氨酸残基揭示了对组氨酸磷酸酶催化机制的新见解。
DOI：
10.1042/bj20121769
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Carpino,Nick
中科院分区：
文献类型：
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作者：
SanLuis,Boris;Nassar,Nicolas;Carpino,Nick
Sts（T细胞受体信号传导抑制因子）-1和Sts-2是负调节TCR（T细胞受体）信号传导途径（包括参与细胞因子产生的那些）的HP（组氨酸磷酸酶）。HP在代谢、发育和细胞内信号传导等多种生物学过程中发挥关键作用。它们在一级序列和底物特异性上有很大的不同，但具有由活性位点残基的不变四联体形成的催化核心。两个组氨酸和两个精氨酸残基在HP活性位点内聚集在一起，并被认为参与两步去磷酸化反应。到目前为止，还没有深入了解任何其他残基，可能发挥重要的功能作用。在本研究中，我们确定和表征内的Sts磷酸酶（Sts-1 Arg 383或Sts-2 Arg 369），这是催化活性和细胞内功能的关键的额外的残基。将Sts-1 Arg 383突变为丙氨酸残基会损害酶的活性，并使Sts-1不能抑制TCR诱导的细胞因子诱导。在替换Arg 383的多个氨基酸中，仅赖氨酸部分地挽救Sts-1的催化活性。虽然Sts-1Arg 383在所有Sts同源物中是保守的，但它仅在HP的两个亚分支中的一个中是保守的。本研究的结果突出了Sts-1磷酸酶活性在调节T细胞活化中的重要作用，并为我们对HP催化活性的理解增加了新的复杂性。
Sts (suppressor of T-cell receptor signalling)-1 and Sts-2 are HPs (histidine phosphatases) that negatively regulate TCR (T-cell receptor) signalling pathways, including those involved in cytokine production. HPs play key roles in such varied biological processes as metabolism, development and intracellular signalling. They differ considerably in their primary sequence and substrate specificity, but possess a catalytic core formed by an invariant quartet of active-site residues. Two histidine and two arginine residues cluster together within the HP active site and are thought to participate in a two-step dephosphorylation reaction. To date there has been little insight into any additional residues that might play an important functional role. In the present study, we identify and characterize an additional residue within the Sts phosphatases (Sts-1 Arg383or Sts-2 Arg369) that is critical for catalytic activity and intracellular function. Mutation of Sts-1 Arg383to an alanine residue compromises the enzyme's activity and renders Sts-1 unable to suppress TCR-induced cytokine induction. Of the multiple amino acids substituted for Arg383, only lysine partially rescues the catalytic activity of Sts-1. Although Sts-1 Arg383is conserved in all Sts homologues, it is only conserved in one of the two sub-branches of HPs. The results of the present study highlight an essential role for Sts-1 phosphatase activity in regulating T-cell activation and add a new dimension of complexity to our understanding of HP catalytic activity.