Pathogenic bacteria utilize specialized macromolecular secretion systems to transport virulence factors across membrane(s) and manipulate their infected host. To date, 11 secretion systems have been identified, including the type IX secretion system (T9SS) associated with human, avian and farmed-fish diseases. As a bacterial secretion system, the T9SS also facilitates gliding motility and the degradation of different macromolecules by the secretion of metabolic enzymes in nonpathogenic bacteria. PorX is a highly conserved protein that regulates the transcription of essential T9SS components and additionally mediates the function of T9SS via direct interaction with PorL, the rotary motor protein of the T9SS. PorX is also a member of a two-component system regulatory cascade, where it serves as the response regulator that relays a signal transduced from a conserved sensor histidine kinase, PorY, to a designated sigma factor. Here, the recombinant expression and purification of PorX homologous proteins from the pathogenic bacterium Porphyromonas gingivalis and the nonpathogenic bacterium Flavobacterium johnsoniae are reported. A bioinformatical characterization of the different domains comprising the PorX protein is also provided, and the crystallization and X-ray analysis of PorX from F. johnsoniae are reported.

中文翻译：

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与 IX 型分泌系统相关的 PorX 反应调节剂的纯化、结晶和晶体学分析

致病细菌利用专门的大分子分泌系统跨膜运输毒力因子并操纵其感染的宿主。迄今为止，已鉴定出 11 种分泌系统，包括与人类、禽类和养殖鱼类疾病相关的 IX 型分泌系统 (T9SS)。作为细菌分泌系统，T9SS还通过非病原菌中代谢酶的分泌促进滑行运动和不同大分子的降解。PorX 是一种高度保守的蛋白质，可调节 T9SS 必需成分的转录，并通过与 T9SS 的旋转运动蛋白 PorL 直接相互作用来介导 T9SS 的功能。PorX 也是双组分系统调节级联的成员，它充当响应调节器，将从保守的传感器组氨酸激酶 PorY 转导的信号中继到指定的 sigma 因子。本文报道了致病菌牙龈卟啉单胞菌和非致病菌约氏黄杆菌中 PorX 同源蛋白的重组表达和纯化。还提供了包含 PorX 蛋白的不同结构域的生物信息学表征，并报告了来自约氏杆菌的 PorX 的结晶和 X 射线分析。