Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China.
Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026, China.
Biochem Biophys Res Commun. 2020 Apr 9;524(3):784-790. doi: 10.1016/j.bbrc.2020.01.146. Epub 2020 Feb 7.
The accessory sec system consisting of seven conserved components is commonly distributed among pathogenic Gram-positive bacteria for the secretion of serine-rich-repeat proteins (SRRPs). Asp1/2/3 protein complex in the system is responsible for both the O-acetylation of GlcNAc and delivering SRRPs to SecA2. However, the molecular mechanism of how Asp1/2/3 transport SRRPs remains unknown. Here, we report the complex structure of Asp1/2/3 from Streptococcus pneumoniae at 2.9 Å. Further functional assays indicated that Asp1/2/3 can stimulate the ATPase activity of SecA2. In addition, the deletion of asp1/2/3 gene resulted in the accumulation of a secreted version of PsrP with an altered glycoform in protoplast fraction of the mutant cell, which suggested the modification/transport coupling of the substrate. Altogether, these findings not only provide structural basis for further investigations on the transport process of SRRPs, but also uncover the indispensable role of Asp1/2/3 in the accessory sec system.
辅助 sec 系统由七个保守成分组成，在致病性革兰氏阳性菌中普遍分布，用于分泌丝氨酸丰富重复蛋白（SRRPs）。该系统中的 Asp1/2/3 蛋白复合物负责 GlcNAc 的 O-乙酰化和将 SRRPs 递送至 SecA2。然而，Asp1/2/3 如何运输 SRRPs 的分子机制尚不清楚。在这里，我们报道了肺炎链球菌 Asp1/2/3 的复合物结构，分辨率为 2.9Å。进一步的功能分析表明，Asp1/2/3 可以刺激 SecA2 的 ATP 酶活性。此外，asp1/2/3 基因的缺失导致突变细胞原生质体部分积累了一种具有改变糖型的分泌型 PsrP，这表明了底物的修饰/运输偶联。总之，这些发现不仅为进一步研究 SRRPs 的运输过程提供了结构基础，而且揭示了 Asp1/2/3 在辅助 sec 系统中的不可或缺作用。
