Houng H S, Venkatesan M M
Department of Enteric Infections, Walter Reed Army Institute of Research, Washington, DC 20307, USA.
Microb Pathog. 1998 Oct;25(4):165-73. doi: 10.1006/mpat.1998.0222.
The form I coding region of Shigella sonnei was cloned and shown to have an operon-like rfb organization. It was found that the 11.0 kb HindIII-XbaI fragment of pHH201 encoding the form I antigen contains 10 contiguous open reading frames (ORF), ORF1 to ORF10. Deletions from either end of pHH201, within ORF1 or ORF10, eliminated form I expression. ORF1 and ORF2 share significant nucleic and amino acids homologies to two ORF's of the Salmonella typhi Vi antigen genes. ORF5 in pHH201 is identical to IS630. pHH2064, derived from pHH201, lacks the IS630 element and can stably express the form I antigen inE. coli HB101. However, pHH2064 is structurally unstable in a S. sonnei form II host. This indicates that the presence of the IS630 gene within the S. sonnei rfb operon may be necessary for the stability of form I expression in S. sonnei. This finding is substantiated by the observation that all virulent S. sonnei isolates examined in this study retained the IS630 element within their rfb operon.
宋内志贺氏菌的I型编码区被克隆，并显示具有类似操纵子的rfb组织。发现编码I型抗原的pHH201的11.0 kb HindIII-XbaI片段包含10个连续的开放阅读框（ORF），即ORF1至ORF10。从pHH201的任一端、ORF1或ORF10内进行缺失，均可消除I型表达。ORF1和ORF2与伤寒沙门氏菌Vi抗原基因的两个ORF具有显著的核酸和氨基酸同源性。pHH201中的ORF5与IS630相同。源自pHH201的pHH2064缺乏IS630元件，并且可以在大肠杆菌HB101中稳定表达I型抗原。然而，pHH2064在宋内志贺氏菌II型宿主中结构不稳定。这表明宋内志贺氏菌rfb操纵子内IS630基因的存在可能是宋内志贺氏菌中I型表达稳定性所必需的。本研究中检测的所有强毒宋内志贺氏菌分离株在其rfb操纵子内均保留了IS630元件，这一观察结果证实了这一发现。
