Sheahan Kerri-Lynn, Cordero Christina L, Satchell Karla J Fullner
Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
EMBO J. 2007 May 16;26(10):2552-61. doi: 10.1038/sj.emboj.7601700. Epub 2007 Apr 26.
Vibrio cholerae RTX is a large multifunctional bacterial toxin that causes actin crosslinking. Due to its size, it was predicted to undergo proteolytic cleavage during translocation into host cells to deliver activity domains to the cytosol. In this study, we identified a domain within the RTX toxin that is conserved in large clostridial glucosylating toxins TcdB, TcdA, TcnA, and TcsL; putative toxins from V. vulnificus, Yersinia sp., Photorhabdus sp., and Xenorhabdus sp.; and a filamentous/hemagglutinin-like protein FhaL from Bordetella sp. In vivo transfection studies and in vitro characterization of purified recombinant protein revealed that this domain from the V. cholerae RTX toxin is an autoprocessing cysteine protease whose activity is stimulated by the intracellular environment. A cysteine point mutation within the RTX holotoxin attenuated actin crosslinking activity suggesting that processing of the toxin is an important step in toxin translocation. Overall, we have uncovered a new mechanism by which large bacterial toxins and proteins deliver catalytic activities to the eukaryotic cell cytosol by autoprocessing after translocation.
霍乱弧菌RTX是一种大型多功能细菌毒素，可导致肌动蛋白交联。由于其大小，预计它在转运到宿主细胞过程中会经历蛋白水解切割，以便将活性结构域递送至胞质溶胶。在本研究中，我们在RTX毒素中鉴定出一个结构域，该结构域在大型梭菌糖基化毒素TcdB、TcdA、TcnA和TcsL中保守；在创伤弧菌、耶尔森氏菌属、发光杆菌属和异小杆线虫属的假定毒素中保守；以及在博德特氏菌属的丝状/血凝素样蛋白FhaL中保守。体内转染研究和纯化重组蛋白的体外表征表明，霍乱弧菌RTX毒素的该结构域是一种自加工半胱氨酸蛋白酶，其活性受细胞内环境刺激。RTX全毒素内的一个半胱氨酸点突变减弱了肌动蛋白交联活性，表明毒素的加工是毒素转运中的一个重要步骤。总体而言，我们发现了一种新机制，大型细菌毒素和蛋白质通过转运后自加工将催化活性递送至真核细胞胞质溶胶。
