Program in Molecular Structure & Function, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
Program in Molecular Structure & Function, Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.
Structure. 2021 May 6;29(5):457-466.e4. doi: 10.1016/j.str.2020.11.019. Epub 2020 Dec 17.
The type IV pilus machinery is a multi-protein complex that polymerizes and depolymerizes a pilus fiber used for attachment, twitching motility, phage adsorption, natural competence, protein secretion, and surface-sensing. An outer membrane secretin pore is required for passage of the pilus fiber out of the cell. Herein, the structure of the tetradecameric secretin, PilQ, from the Pseudomonas aeruginosa type IVa pilus system was determined to 4.3 Å and 4.4 Å resolution in the presence and absence of C symmetric spikes, respectively. The heptameric spikes were found to be two tandem C-terminal domains of TsaP. TsaP forms a belt around PilQ and while it is not essential for twitching motility, overexpression of TsaP triggers a signal cascade upstream of PilY1 leading to cyclic di-GMP up-regulation. These results resolve the identity of the spikes identified with Proteobacterial PilQ homologs and may reveal a new component of the surface-sensing cyclic di-GMP signal cascade.
IV 型菌毛机械是一个多蛋白复合物，用于聚合和解聚菌毛纤维，菌毛纤维用于附着、蠕动运动、噬菌体吸附、自然感受能力、蛋白质分泌和表面感应。外膜分泌孔是菌毛纤维穿出细胞所必需的。本文确定了铜绿假单胞菌 IVa 型菌毛系统中十四聚体分泌蛋白 PilQ 的结构，在有和没有 C 对称刺突的情况下，分辨率分别为 4.3Å 和 4.4Å。发现七聚体刺突是 TsaP 的两个串联 C 末端结构域。TsaP 围绕 PilQ 形成一个带，虽然它不是蠕动运动所必需的，但 TsaP 的过表达会触发 PilY1 上游的信号级联，导致环二鸟苷酸的上调。这些结果确定了与 Proteobacterial PilQ 同源物识别的刺突的身份，并可能揭示表面感应环二鸟苷酸信号级联的一个新组成部分。
