Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL 35294, United States; Department of Chemistry, The University of Alabama at Birmingham, Birmingham, AL 35294, United States.
Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, AL 35294, United States.
Comput Biol Chem. 2020 Apr;85:107228. doi: 10.1016/j.compbiolchem.2020.107228. Epub 2020 Feb 3.
Calreticulin (CRT) is localized to and has functions in multiple cellular compartments, including the cell surface, the endoplasmic reticulum, and the extracellular matrix. Mutagenesis studies have identified several residues on a concave β-sheet surface of CRT critical for CRT binding to carbohydrate and other proteins/peptides. How the mutations of these key residues in CRT affect the conformation and dynamics of CRT, further influencing CRT binding to carbohydrates and other proteins to signal the important biological activities remain unknown. In this study, we investigated the effect of three key point mutations (C105A, C137A and W319A) on CRT conformation and dynamics via atomistic molecular dynamics simulations. Results show that these three key residues mutations induced the changes of CRT local backbone flexibility and secondary structure of CRT N-domain, which could further affect CRT's binding activity. C137A mutation led to dramatic decrease of the overall size of CRT due to the P-domain fold back to the globular domain and formed new inter-domain contacts, which can cause blockage of CRT's binding with other large substrates. Furthermore, for CRT concave β-strand surface patch containing lectin binding site, CRT C105A, C137A and W319A point mutation resulted in the changes in solvent accessible surface area, key residues' side chain atom positions and dynamical correlated motions between residues. All these changes could directly affect CRT binding behavior. Results of this study provide molecular and structural insights into understanding the role of key residues of CRT in its binding behavior.
钙网蛋白（CRT）定位于多个细胞区室，包括细胞表面、内质网和细胞外基质，并具有多种功能。突变研究已经确定了 CRT 上一个凹面β-折叠表面上的几个关键残基对于 CRT 与碳水化合物和其他蛋白质/肽的结合至关重要。这些 CRT 关键残基的突变如何影响 CRT 的构象和动力学，进一步影响 CRT 与碳水化合物和其他蛋白质的结合以发出重要的生物学活性仍然未知。在这项研究中，我们通过原子分子动力学模拟研究了三个关键点突变（C105A、C137A 和 W319A）对 CRT 构象和动力学的影响。结果表明，这三个关键残基的突变导致 CRT 局部骨架灵活性和 CRT N 结构域二级结构的变化，这可能进一步影响 CRT 的结合活性。C137A 突变导致 CRT 整体尺寸的急剧减小，因为 P 结构域折叠回到球蛋白结构域并形成新的结构域间接触，这可能导致 CRT 与其他大底物的结合受阻。此外，对于 CRT 包含凝集素结合位点的凹面β-链表面斑块，CRT C105A、C137A 和 W319A 点突变导致溶剂可及表面积、关键残基侧链原子位置以及残基之间动态相关运动的变化。所有这些变化都可能直接影响 CRT 的结合行为。这项研究的结果提供了分子和结构方面的见解，有助于理解 CRT 关键残基在其结合行为中的作用。
