Department of Biophysics, National Institute of Mental Health and Neuro Sciences (NIMHANS), Bengaluru, India.
Department of Microbiology, National Institute of Mental Health and Neuro Sciences (NIMHANS), Bengaluru, India.
Protein Sci. 2023 Sep;32(9):e4737. doi: 10.1002/pro.4737.
Methicillin-resistant Staphylococcus aureus (MRSA) causes life-threatening human infections. Bacteriophage-encoded endolysins degrade the cell walls of Gram-positive bacteria by selectively hydrolyzing the peptidoglycan layer and thus are promising candidates to combat bacterial infections. PlyGRCS, the S. aureus-specific bacteriophage endolysin, contains a catalytic CHAP domain and a cell-wall binding SH3_5 domain connected by a linker. Here, we show the crystal structure of full-length PlyGRCS refined to 2.1 Å resolution. In addition, a serendipitous finding revealed that PlyGRCS binds to cold-shock protein C (CspC) by interacting with its CHAP and SH3_5 domains. CspC is an RNA chaperone that plays regulatory roles by conferring bacterial adaptability to various stress conditions. PlyGRCS has substantial lytic activity against S. aureus and showed only minimal change in its lytic activity in the presence of CspC. Whereas the PlyGRCS-CspC complex greatly reduced CspC-nucleic acid binding, the aforesaid complex may downregulate the CspC function during bacterial infection. Overall, the crystal structure and biochemical results of PlyGRCS provide a molecular basis for the bacteriolytic activity of PlyGRCS against S. aureus.
耐甲氧西林金黄色葡萄球菌（MRSA）可引起危及生命的人类感染。噬菌体编码的内溶素通过选择性水解肽聚糖层来降解革兰氏阳性菌的细胞壁，因此是对抗细菌感染的有前途的候选药物。PlyGRCS 是一种针对金黄色葡萄球菌的噬菌体内溶素，包含一个催化 CHAP 结构域和一个通过连接子连接的细胞壁结合 SH3_5 结构域。在这里，我们展示了全长 PlyGRCS 的晶体结构，分辨率为 2.1Å。此外，一个偶然的发现表明，PlyGRCS 通过与 CHAP 和 SH3_5 结构域相互作用与冷休克蛋白 C（CspC）结合。CspC 是一种 RNA 伴侣，通过赋予细菌对各种应激条件的适应性来发挥调节作用。PlyGRCS 对金黄色葡萄球菌具有很强的溶菌活性，并且在存在 CspC 的情况下其溶菌活性仅发生微小变化。尽管 PlyGRCS-CspC 复合物大大降低了 CspC-核酸结合，但上述复合物可能在细菌感染过程中下调 CspC 功能。总体而言，PlyGRCS 的晶体结构和生化结果为 PlyGRCS 针对金黄色葡萄球菌的溶菌活性提供了分子基础。
