Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14850, USA.
FEBS Lett. 2012 Nov 16;586(22):3956-61. doi: 10.1016/j.febslet.2012.09.041. Epub 2012 Oct 16.
The CRISPR system is an adaptive RNA-based microbial immune system against invasive genetic elements. CasB is an essential protein component in Type I-E Cascade. Here, we characterize CasB proteins from three different organisms as non-specific nucleic acid binding proteins. The Thermobifida fusca CasB crystal structure reveals conserved positive surface charges, which we show are important for its nucleic acid binding function. EM docking reveals that CasB dimerization aligns individual nucleic acid binding surfaces into a curved, elongated binding surface inside Type I-E Cascade, consistent with the putative functions of CasB in ds-DNA recruitment and crRNA-DNA duplex formation steps.
CRISPR 系统是一种适应性的基于 RNA 的微生物免疫系统，可对抗入侵的遗传元件。CasB 是 I 型-E 级联反应中的一种必需的蛋白质组成部分。在这里，我们将三种不同生物的 CasB 蛋白鉴定为非特异性核酸结合蛋白。热纤梭菌 CasB 晶体结构揭示了保守的正表面电荷，我们表明这些电荷对于其核酸结合功能很重要。EM 对接揭示了 CasB 二聚体将单个核酸结合表面排列成 I 型-E 级联反应内部的弯曲、细长的结合表面，这与 CasB 在 ds-DNA 募集和 crRNA-DNA 双链体形成步骤中的假定功能一致。
