铕对小麦根细胞钙调素及NAD激酶的影响研究

研究了Eu对小麦根细胞内钙调素的含量和活性以及对受钙调素调控的专一性酶NAD激酶的影响。结果表明，Eu^3＋有类似Ca^2＋的作用，影响受Ca^2＋浓度调控的信号系统关键蛋白——钙调素的活性和含量变化。从而引起钙调素调控酶NAD激酶的活性改变，最终影响细胞内生理生化过程。认为稀土离子对生物体的Hormesis效应町能与稀土离子对细胞信号传递系统的影响有关，稀土离子可能通过影响细胞信号系统来调节细胞内的各种生理生化变化，形成稀土元素生物效应的多样性特征。     

CHARMM36 all‐atom additive protein force field: Validation based on comparison to NMR data

Protein structure and dynamics can be characterized on the atomistic level with both nuclear magnetic resonance (NMR) experiments and molecular dynamics (MD) simulations. Here, we quantify the ability of the recently presented CHARMM36 (C36) force field (FF) to reproduce various NMR observables using MD simulations. The studied NMR properties include backbone scalar couplings across hydrogen bonds, residual dipolar couplings (RDCs) and relaxation order parameter, as well as scalar couplings, RDCs, and order parameters for side‐chain amino‐ and methyl‐containing groups. It is shown that the C36 FF leads to better correlation with experimental data compared to the CHARMM22/CMAP FF and suggest using C36 in protein simulations. Although both CHARMM FFs contains the same nonbond parameters, our results show how the changes in the internal parameters associated with the peptide backbone via CMAP and the χ₁ and χ₂ dihedral parameters leads to improved treatment of the analyzed nonbond interactions. This highlights the importance of proper treatment of the internal covalent components in modeling nonbond interactions with molecular mechanics FFs. © 2013 Wiley Periodicals, Inc.     

Application of plug–plug technique to ACE experiments for discovery of peptides binding to a larger target protein: A model study of calmodulin‐binding fragments selected from a digested mixture of reduced BSA

To discover peptide ligands that bind to a target protein with a higher molecular mass, a concise screening methodology has been established, by applying a “plug–plug” technique to ACE experiments. Exploratory experiments using three mixed peptides, mastoparan‐X, β‐endorphin, and oxytocin, as candidates for calmodulin‐binding ligands, revealed that the technique not only reduces the consumption of the protein sample, but also increases the flexibility of the experimental conditions, by allowing the use of MS detection in the ACE experiments. With the plug–plug technique, the ACE–MS screening methodology successfully selected calmodulin‐binding peptides from a random library with diverse constituents, such as protease digests of BSA. Three peptides with K_d values between 8–147 μM for calmodulin were obtained from a Glu‐C endoprotease digest of reduced BSA, although the digest showed more than 70 peaks in its ACE–MS electropherogram. The method established here will be quite useful for the screening of peptide ligands, which have only low affinities due to their flexible chain structures but could potentially provide primary information for designing inhibitors against the target protein.     

钙调蛋白抑制剂预测模型研究

选用30个结构多样的caM抑制剂分子作为数据集,采用多元线性回归(MLR)方法及主成分回归分析(PCA)方法对每个化合物的194个分子参数进行回归分析,分别建立了各自的最优预测模型.结果表明:多元线性回归分析方法所建模型与主成分回归所建模型相对比,发现逐步筛选法为最优建模方法?该方法所建模型统计结果良好(R2=0.952,SEE为0.289),应用于检验集时结果也比较令人满意(R2=0.941,SEP为0.295),模型表现出较强的可靠性和预测性.     

Detailed Evidence for an Unparalleled Interaction Mode between Calmodulin and Orai Proteins

Calmodulin (CaM) binds most of its targets by wrapping around an amphipathic α‐helix. The N‐terminus of Orai proteins contains a conserved CaM‐binding segment but the binding mechanism has been only partially characterized. Here, microscale thermophoresis (MST), surface plasmon resonance (SPR), and atomic force microscopy (AFM) were employed to study the binding equilibria, the kinetics, and the single‐molecule interaction forces involved in the binding of CaM to the conserved helical segments of Orai1 and Orai3. The results consistently indicated stepwise binding of two separate target peptides to the two lobes of CaM. An unparalleled high affinity was found when two Orai peptides were dimerized or immobilized at high lateral density, thereby mimicking the close proximity of the N‐termini in native Orai oligomers. The analogous experiments with smooth muscle myosin light chain kinase (smMLCK) showed only the expected 1:1 binding, confirming the validity of our methods.     

Temperature dependences on the infrared spectra of some proteins

Recent developments of FT-IR and computer techniques made it possible to detect minute changes (temperature dependences etc.) in the infrared spectra of proteins in aqueous solution.In this paper we studied temperature dependences of the amide I and I bands of ribonuclease A (RNase A), calmodulin (CaM), and Ca²⁺-bound CaM in H₂O and D₂O solutions between 28°C and 70°C using the difference-spectrum and Fourier self-deconvolution techniques.     

钙调素与靶蛋白结合模式的多样性

钙调素(CaM)通过与数百种靶蛋白结合,调节众多钙信号通路参与的生理活动。钙调素与靶蛋白的结合模式也是多种多样的,数年前就有多篇这方面的综述发表,最近的一篇发表于2006年。这之后的5、6年,又有大量钙调素-靶蛋白复合体的结构以及新型的结合模式发表,这其中就包括本实验室发表的钙调素与钙调蛋白磷酸酶(CN)的钙调素结合区(CBD)结合的晶体结构,为不同于经典模式的X形二聚体。本文在前人综述的基础上,结合本实验室的成果,以及其他近5、6年新发表的结构,从经典包围型、其他包围型、伸展型、IQ基序相关、二聚体型、大分子参与的结合模式共6个类别,讨论了30多种钙调素-靶蛋白复合体的结构。这些多样的结合模式为钙调素调节功能的多样性提供了结构基础,也为解析结构未知的钙调素-靶蛋白复合体提供了启示。     

基体辅助激光解吸电离飞行时间质谱法测定钙调素的分子量

近几年来，由于各种“软”电离技术的发展和应用「‘，’‘，为利用质谱分析生物大分子提供了一条十分有效的途径［‘j，其中基体辅助激光解吸电离飞行时间质谱法（MALDI－TOF－MS）是最有前途的技术之一D‘．钙调素（CaM）是动植物中普遍存在的多功能的胞内钙受体蛋白，参与调控许多生理反应［”．最近几年也在细胞外区域发现了钙调素及其功能［”．钙调素分子量的准确、快速测定是钙调素性质、结构和功能研究的首要问题．目前CaM分子量的测定大多采用SDS－PAGE、凝胶过滤和沉淀平衡等方法，例如对牛脑CaM分子量的SDS－PAGE测…