CHARACTERIZATION OF THE SHIGELLA-FLEXNERI IPGD AND IPGF GENES, WHICH ARE LOCATED IN THE PROXIMAL PART OF THE MXI LOCUS
CHARACTERIZATION OF THE SHIGELLA-FLEXNERI IPGD AND IPGF GENES, WHICH ARE LOCATED IN THE PROXIMAL PART OF THE MXI LOCUS
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DOI：
10.1128/iai.61.5.1707-1714.1993
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发表时间：
1993-05-01
影响因子：
3.1
通讯作者：
PARSOT, C
中科院分区：
文献类型：
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作者：
ALLAOUI, A;MENARD, R;PARSOT, C
福氏志贺氏菌的入侵过程需要Ipa蛋白的合成，并由位于Ipa操纵子上游的mxi和spa基因编码的特定因子分泌Ipa蛋白。我们在这里报道了位于mxi位点5'端的ipgD、ipgE和ipgF基因的特征。对具有高水平碱性磷酸酶活性的IpgF- phoa融合体的分析证实了IpgF序列中检测到的经典信号序列的功能。通过插入非极性盒，ipgD和ipgF基因在大毒力质粒上分别失活；由此构建的每一个ipgD和ipgF突变体都显示出与野生型菌株相同的侵袭性表型，并且也能够在豚鼠中引起角膜结膜炎。因此，位于mxi位点近端部分的两个基因似乎不直接参与入侵。野生型和ipgD菌株的浓缩培养上清分析表明，ipgD突变体中没有分泌一种多肽，其大小与预测的ipgD蛋白（60 kDa）一致。
The Shigella flexneri invasion process requires the synthesis of the Ipa proteins and their secretion by specific factors encoded by the mxi and spa genes, which are clustered upstream from the ipa operon. We report here the characterization of the ipgD, ipgE, and ipgF genes, which are located in the 5' end of the mxi locus. Analysis of IpgF-PhoA fusions endowed with high levels of alkaline phosphatase activity confirmed the functionality of a classical signal sequence detected in the sequence of IpgF. The ipgD and ipgF genes were each inactivated on the large virulence plasmid by insertion of a nonpolar cassette; each of the ipgD and ipgF mutants thus constructed showed the same invasive phenotype as the wild-type strain and was also able to provoke keratoconjunctivitis in guinea pigs. It thus appears that two genes located at the ipa-proximal part of the mxi locus are not directly involved in invasion. Analysis of concentrated culture supernatants of the wild-type and ipgD strains indicated that secretion of one polypeptide, whose size was consistent with that predicted for the IpgD protein (60 kDa), was abolished in the ipgD mutant.