Burall Laurel S, Liu Zhi, Rank Roger, Bavoil Patrik M
Department of Biomedical Sciences, University of Maryland Baltimore, Dental School, 666 W. Baltimore St., Baltimore, MD 21201, USA.
Microbes Infect. 2007 Jun;9(7):873-80. doi: 10.1016/j.micinf.2007.03.006. Epub 2007 Mar 18.
Variants of an ilp (invasin-like protein) gene have been identified previously in Chlamydia caviae and in Chlamydia suis. The C. caviae ilp gene is interrupted by two frame shift mutations while the C. suis gene is intact. Characterization of the ilp gene in C. caviae passaged minimally in vitro showed that the two frameshift mutations were present in the original isolates. The gentamicin protection assay was used to determine if E. coli bacteria expressing the intact C. suis ilp could adhere to or invade HEp-2 cells. While inv+ clones showed increased adherence and invasion, no increase in adherence or invasion was observed for ilp+ clones. However, these clones were found to produce detectable amounts of ilp transcript. In a 48 h time course of C. suis culture, ilp transcript was initially detected at 8 h, peaked at 16 h, and declined subsequently. Antibodies specifically recognizing the putative functional domain of Ilp failed to detect any ilp-specific gene product in either E. coli or C. suis cultures. These data suggest that ilp does not encode a functional protein and raise questions about how ilp was introduced and maintained in Chlamydia.
此前已在豚鼠衣原体和猪衣原体中鉴定出一种侵袭素样蛋白（ilp）基因的变体。豚鼠衣原体的ilp基因被两个移码突变打断，而猪衣原体的基因是完整的。对在体外极少传代的豚鼠衣原体中ilp基因的特征分析表明，原始分离株中存在这两个移码突变。采用庆大霉素保护试验来确定表达完整猪衣原体ilp的大肠杆菌是否能黏附或侵入人喉表皮样癌细胞（HEp-2细胞）。虽然inv+克隆显示出黏附力和侵袭力增强，但ilp+克隆未观察到黏附或侵袭力增加。然而，发现这些克隆产生可检测量的ilp转录本。在猪衣原体培养的48小时时间进程中，ilp转录本最初在8小时被检测到，在16小时达到峰值，随后下降。特异性识别Ilp假定功能域的抗体未能在大肠杆菌或猪衣原体培养物中检测到任何ilp特异性基因产物。这些数据表明ilp不编码功能性蛋白质，并引发了关于ilp如何在衣原体中引入和维持的问题。
