Department of Biochemistry, Bose Institute, P-1/12, CIT Scheme VII M, Kolkata, West Bengal 700054, India.
Department of Biochemistry and Biophysics, University of Kalyani, Kalyani, West Bengal, India.
Int J Biol Macromol. 2020 May 15;151:1287-1298. doi: 10.1016/j.ijbiomac.2019.10.175. Epub 2019 Nov 18.
SaCyp, a cyclophilin having 197 amino acid residues, acts both as a protein-folding catalyst and a virulence factor in Staphylococcus aureus. Interestingly, a region, homologous to the SaCyp region carrying 121-148 amino acid residues, is present in many putative cyclophilins but absent in well-studied cyclophilins. To determine the exact roles of this unusual region in SaCyp and related proteins, we have investigated a deletion mutant (rCypΔ) of a recombinant SaCyp (rCyp) using various probes. The data reveal that rCypΔ has significantly less catalytic activity and possesses altered structure and hydrophobic surface compared to rCyp. Conversely, the deletion substantially increased inhibitor binding affinity and altered the shape of rCyp. However, both proteins were unfolded by a non-two-state mechanism in the presence of urea. Additionally, the stability of rCyp was significantly reduced due to the deletion of the residues 121-148. Our MD simulation study also indicated the considerable alteration in structure, shape, and fluctuations of SaCyp due to the removal of the region carrying 121-148 residues. Hence, the atypical region located in SaCyp might be vital for maintaining its unique structure, function, stability, and shape.
SaCyp 是一种含有 197 个氨基酸残基的亲环蛋白，它既是一种蛋白质折叠催化剂，也是金黄色葡萄球菌的毒力因子。有趣的是，在许多推定的亲环蛋白中存在一个与 SaCyp 区域同源的区域，该区域携带 121-148 个氨基酸残基，但在研究充分的亲环蛋白中不存在。为了确定这个不寻常区域在 SaCyp 和相关蛋白中的确切作用，我们使用各种探针研究了重组 SaCyp(rCyp)的缺失突变体(rCypΔ)。数据表明，与 rCyp 相比，rCypΔ的催化活性显著降低，结构和疏水性表面发生改变。相反，缺失显著增加了抑制剂的结合亲和力，并改变了 rCyp 的形状。然而，在存在脲的情况下，两种蛋白质都通过非两态机制展开。此外，由于缺失 121-148 个残基，rCyp 的稳定性显著降低。我们的 MD 模拟研究还表明，由于去除了携带 121-148 个残基的区域，SaCyp 的结构、形状和波动发生了相当大的改变。因此，位于 SaCyp 中的非典型区域对于维持其独特的结构、功能、稳定性和形状可能至关重要。
