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目的为证实调控ｉｐａＢＣＤ表达除侵袭质粒上的两个正性调控基因ｖｉｒＦ和ｉｎｖＥ外，染色体上也可能存在与ｉｎｖＥ共同参与促进ｉｐａ基因表达的因子。方法应用低拷贝克隆载体ｐＡ－ＣＹＣ１８４，在大肠杆菌构建福氏志贺氏菌染色体基因文库。经半乳糖苷酶活性测定、分子杂交等筛选，获得一株能增进上皮细胞侵袭性基因ｉｐａＢ表达的ＤＮＡ分子克隆ｐＱ４４５。结果该片段约为４．３ｋｂ长，ＤＮＡ序列分析表明有两个完整的开放阅读框架（ＯＲＦ），经插入缺失突变发现，其中一个ＯＲＦ的表达产物能增加ｉｐａＢ的活性，为ｉｐａ正性调节因子，定名为ｃｒｉＡ。ｃｒｉＡ基因位于细菌染色体８７．３分处，志贺菌属大多菌群都携带该基因。ｃｒｉＡ约１４３８ｂｐ，编码４７６个氨基酸残基的酸性蛋白，分子量约５２６００。结论ＣｒｉＡ蛋白可能凭借其２６８～２９８位和３２０～３４１位两处的氨基酸残基位点亮氨酸拉链区结构，在蛋白相互作用中调节侵袭性基因的表达
OBJECTIVE: To confirm that regulation of ipaBCD expression in addition to the two virulence-regulating genes virF and invE on the plasmid, there may also be factors on the chromosome that are involved in the promotion of ipa gene expression. Methods The low copy cloning vector pA-CYC184 was used to construct the gene library of Shigella flexneri in Escherichia coli. After screening by galactosidase activity assay and molecular hybridization, we obtained a DNA molecular clone pQ445 that can promote ipaB expression in epithelial cells. Results The fragment was about 4.3kb long. The DNA sequence analysis showed that there are two complete open reading frames (ORFs). The insertion deletion mutation found that one of the ORFs could increase ipaB activity, , Named criA. The criA gene is located at 87.3 of the bacterial chromosome, and most of the Shigella bacteria carry this gene. criA about 1438bp, encoding acid protein 476 amino acid residues, the molecular weight of about 52600. Conclusion CriA protein may regulate leucine zipper domain structure by virtue of its amino acid residues at positions 268 ~ 298 and 320 ~ 341, and regulate the expression of aggressive genes in protein interaction