An Inherent Difference between Serine and Threonine Phosphorylation: Phosphothreonine Strongly Prefers a Highly Ordered, Compact, Cyclic Conformation
An Inherent Difference between Serine and Threonine Phosphorylation: Phosphothreonine Strongly Prefers a Highly Ordered, Compact, Cyclic Conformation
复制标题
DOI：
10.1021/acschembio.3c00068
复制
发表时间：
2023-08-18
影响因子：
4
通讯作者：
Zondlo，Neal J.
中科院分区：
文献类型：
--
作者：
Pandey，Anil K.;Ganguly，Himal K.;Zondlo，Neal J.
激酶和磷酸酶对蛋白质的磷酸化和去磷酸化是细胞反应和功能的核心。丝氨酸和苏氨酸磷酸化的结构影响进行了研究，在肽和蛋白质，圆二色性，NMR光谱，生物信息学分析的PDB，小分子X-射线晶体学，和计算研究。丝氨酸和苏氨酸残基的磷酸化诱导其生理上更重要的双阴离子形式的大量构象限制。苏氨酸在磷酸化后表现出特别强的无序到有序的转变，双阴离子磷酸苏氨酸优先采用具有限制性构象的环状构象。（θ =-60 °）通过三种非共价相互作用稳定：一个强的残基内磷酸-酰胺氢键，连续羰基之间的n → π* 相互作用，磷酸Oγ孤对电子与C-Hβ反键轨道之间存在n → σ* 相互作用，限制了χ 2侧链构象.脯氨酸是一种独特的典型氨基酸，其主链上的共价环化。磷酸苏氨酸可以通过非共价相互作用模拟脯氨酸的主链环化。双阴离子磷酸苏氨酸的优选扭转是：α，β =聚脯氨酸II螺旋> α-螺旋（β = −60°）; χ1=g-; χ2 β +115°（重叠的C-H/O-P键）。这种结构特征在不同的蛋白质中观察到，包括在蛋白激酶的激活环和蛋白质-蛋白质相互作用中。总的来说，这些结果表明了蛋白质中苏氨酸与丝氨酸磷酸化位点的差异使用和进化的结构基础，丝氨酸磷酸化通常诱导较小的变阻器样变化，而苏氨酸磷酸化促进蛋白质中较大的阶跃功能样开关。
Phosphorylation and dephosphorylation of proteins by kinases and phosphatases are central to cellular responses and function. The structural effects of serine and threonine phosphorylation were examined in peptides and in proteins, by circular dichroism, NMR spectroscopy, bioinformatics analysis of the PDB, small-molecule X-ray crystallography, and computational investigations. Phosphorylation of both serine and threonine residues induces substantial conformational restriction in their physiologically more important dianionic forms. Threonine exhibits a particularly strong disorder-to-order transition upon phosphorylation, with dianionic phosphothreonine preferentially adopting a cyclic conformation with restricted ϕ (ϕ ∼ −60°) stabilized by three noncovalent interactions: a strong intraresidue phosphate-amide hydrogen bond, an n → π* interaction between consecutive carbonyls, and an n → σ* interaction between the phosphate Oγ lone pair and the antibonding orbital of C–Hβ that restricts the χ2side-chain conformation. Proline is unique among the canonical amino acids for its covalent cyclization on the backbone. Phosphothreonine can mimic proline’s backbone cyclization via noncovalent interactions. The preferred torsions of dianionic phosphothreonine are ϕ,ψ = polyproline II helix > α-helix (ϕ ∼ −60°); χ1=g–; χ2∼ +115° (eclipsed C–H/O–P bonds). This structural signature is observed in diverse proteins, including in the activation loops of protein kinases and in protein–protein interactions. In total, these results suggest a structural basis for the differential use and evolution of threonine versus serine phosphorylation sites in proteins, with serine phosphorylation typically inducing smaller, rheostat-like changes, versus threonine phosphorylation promoting larger, step function-like switches, in proteins.