Conformational and thermodynamic properties of peptide binding to the human S100P protein
Conformational and thermodynamic properties of peptide binding to the human S100P protein
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DOI：
10.1110/ps.0202202
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发表时间：
2002-06-01
期刊：
影响因子：
8
通讯作者：
Makhatadze, GI
中科院分区：
文献类型：
--
作者：
Gribenko, AV;Guzmán-Casado, M;Makhatadze, GI
S100P是S 100钙结合蛋白亚家族的成员，被认为与多种疾病有关，特别是S100P表达的解除调控在前列腺癌和乳腺癌中已被报道。在此之前，我们研究了金属结合对S100P构象性质的影响，并提出S100P可能具有钙离子构象开关的作用。在这项研究中，我们使用荧光光谱、圆二色谱和等温滴定量热法，以模型肽蜂毒素为模型来表征S100P的靶向识别特性。基于这些实验数据，我们证明S100P和蜂毒素可以以钙依赖和非依赖的方式相互作用。钙不依赖的结合发生在低亲和力(K-d约为0.2 mM)，每个S100P二聚体有四个蜂毒素分子的化学计量比，推测是由酸性蛋白质和碱性多肽之间良好的静电相互作用驱动的。相反，依赖钙离子的蜂毒素与S100P的结合具有高亲和力(K-d约为5um)，每个S100P二聚体具有两个分子的蜂毒素化学计量比，似乎具有正的协同性，并由疏水相互作用驱动。此外，依赖于钙离子的S100P-蜂毒素复合体的形成伴随着显著的构象变化：蜂毒素在溶液中原本是无结构的，但在与钙-S100P相互作用时呈螺旋构象。这些结果支持S100P中钙离子依赖的构象开关的功能靶标识别模型。
S100P is a member of the S 100 subfamily of calcium-binding proteins that are believed to be associated with various diseases, and in particular deregulation of S100P expression has been documented for prostate and breast cancer. Previously, we characterized the effects of metal binding on the conformational properties of S100P and proposed that S100P could function as a Ca2+ conformational switch. In this study we used fluorescence and CD spectroscopies and isothermal titration calorimetry to characterize the target-recognition properties of S100P using a model peptide, melittin. Based on these experimental data we show that S100P and melittin can interact in a Ca2+-dependent and -independent manner. Ca2+-independent binding occurs with low affinity (K-d approximate to 0.2 mM), has a stoichiometry of four melittin molecules per S100P dimer and is presumably driven by favorable electrostatic interactions between the acidic protein and the basic peptide. In contrast, Ca2+-dependent binding of melittin to S100P occurs with high affinity (K-d approximate to 5 muM) has a stoichiometry of two molecules of melittin per S100P dimer, appears to have positive cooperativity, and is driven by hydrophobic interactions. Furthermore, Ca2+-dependent S100P-melittin complex formation is accompanied by significant conformational changes: Melittin, otherwise unstructured in solution, adopts a helical conformation upon interaction with Ca2+-S100P. These results support a model for the Ca2+-dependent conformational switch in S100P for functional target recognition.