School of Life Sciences and Center of Novel Biomaterials, The Chinese University of Hong Kong, Shatin, Hong Kong SAR 999077, China.
School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR 999077, China.
Toxins (Basel). 2022 Nov 23;14(12):823. doi: 10.3390/toxins14120823.
The crystal protein Cry5B, a pore-forming protein produced by the soil bacterium , has been demonstrated to have excellent anthelmintic activity. While a previous structure of the three-domain core region of Cry5B(112-698) had been reported, this structure lacked a key N-terminal extension critical to function. Here we report the structure of Cry5B(27-698) containing this N-terminal extension. This new structure adopts a distinct quaternary structure compared to the previous Cry5B(112-698) structure, and also exhibits a change in the conformation of residues 112-140 involved in linking the N-terminal extension to the three-domain core by forming a random coil and an extended α-helix. A role for the N-terminal extension is suggested based on a computational model of the tetramer with the conformation of residues 112-140 in its alternate α-helix conformation. Finally, based on the Cry5B(27-698) structure, site-directed mutagenesis studies were performed on Tyr495, which revealed that having an aromatic group or bulky group at this residue 495 is important for Cry5B toxicity.
晶体蛋白 Cry5B 是一种由土壤细菌产生的孔形成蛋白，已被证明具有优异的驱虫活性。虽然之前已经报道了 Cry5B 的三结构域核心区域（112-698）的结构，但该结构缺乏对功能至关重要的关键 N 端延伸。在这里，我们报告了包含该 N 端延伸的 Cry5B（27-698）的结构。与之前的 Cry5B（112-698）结构相比，这个新结构采用了独特的四级结构，并且还表现出参与连接 N 端延伸到三结构域核心的残基 112-140 的构象变化，通过形成无规卷曲和伸展的α-螺旋。基于四聚体的计算模型，该 N 端延伸的作用暗示了残基 112-140 的构象处于其交替α-螺旋构象。最后，基于 Cry5B（27-698）结构，对 Tyr495 进行了定点突变研究，结果表明该残基 495 上有芳香基团或大基团对于 Cry5B 的毒性很重要。
