Lee Robert B, Hassane Duane C, Cottle Daniel L, Pickett Carol L
Department of Microbiology, Immunology, and Molecular Genetics, School of Medicine, University of Kentucky, Lexington, Kentucky 40536, USA.
Infect Immun. 2003 Sep;71(9):4883-90. doi: 10.1128/IAI.71.9.4883-4890.2003.
Campylobacter jejuni produces a toxin, called cytolethal distending toxin (CDT), which causes direct DNA damage leading to invocation of DNA damage checkpoint pathways. The affected cells arrest in G(1) or G(2) and eventually die. CDT consists of three protein subunits, CdtA, CdtB, and CdtC, with CdtB recently identified as a nuclease. However, little is known about the functions of CdtA or CdtC. In this work, enzyme-linked immunosorbent assay-based experiments were used to show, for the first time, that both CdtA and CdtC bound with specificity to the surface of HeLa cells, whereas CdtB did not. Varying the order of the addition of subunits for reconstitution of the holotoxin had no effect on activity. In addition, mutants containing deletions of conserved regions of CdtA and CdtC were able to bind to the surface of HeLa cells but were not able to participate in holotoxin assembly. Finally, both Cdt mutant subunits were able to effectively compete with CDT holotoxin in the HeLa cell binding assay.
空肠弯曲菌产生一种名为细胞致死性膨胀毒素（CDT）的毒素，该毒素会导致直接的DNA损伤，从而引发DNA损伤检查点通路。受影响的细胞停滞在G1或G2期并最终死亡。CDT由三个蛋白质亚基CdtA、CdtB和CdtC组成，最近发现CdtB是一种核酸酶。然而，对于CdtA或CdtC的功能知之甚少。在这项研究中，首次使用基于酶联免疫吸附测定的实验表明，CdtA和CdtC均特异性结合到HeLa细胞表面，而CdtB则不然。改变用于重组全毒素的亚基添加顺序对活性没有影响。此外，含有CdtA和CdtC保守区域缺失的突变体能够结合到HeLa细胞表面，但不能参与全毒素组装。最后，在HeLa细胞结合试验中，两种Cdt突变亚基都能够有效地与CDT全毒素竞争。
