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首页> 外文期刊>Journal of bacteriology >Translocation of capsular polysaccharides in pathogenic strains of Escherichia coli requires a 60-kilodalton periplasmic protein.
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Translocation of capsular polysaccharides in pathogenic strains of Escherichia coli requires a 60-kilodalton periplasmic protein.

机译：大肠杆菌病原性菌株中荚膜多糖的移位需要60千达尔顿周质蛋白。

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摘要

An 11.6-kilobase (kb) region of a 34-kb fragment of Escherichia coli DNA that encodes the K1 capsular polysaccharide genes is necessary for translocation of the K1 polysaccharide to the bacterial cell surface. This 11.6-kb region contains a gene, kpsD, encoding a 60-kilodalton protein. The kpsD gene was localized to a 2.4-kb PstI-BamHI fragment. Cells harboring a Tn1000 insertion in kpsD did not synthesize the 60-kilodalton protein and did not express polysaccharide on the cell surface. Immunodiffusion and rocket immunoelectrophoresis of cell extracts, however, demonstrated that K1 polysaccharide was synthesized by these cells. We present evidence that the kpsD gene product is synthesized as a precursor and that the processed form is located in the periplasmic space. Analysis of alkaline phosphatase activity of a kpsD-phoA fusion demonstrated that kpsD expression was under positive regulation. A 260-base-pair AluI fragment located within the kpsD coding sequence was used as a probe and was found to hybridize to chromosomal DNA from E. coli that synthesizes the K2, K5, K7, K12, and K13 capsular polysaccharides but not K3 and K100. These results suggest that the kpsD gene product may be required for export not only of K1 but for other K antigens as well.
机译：编码K1荚膜多糖基因的大肠杆菌DNA的34 kb片段的11.6千碱基（kb）区是将K1多糖转运到细菌细胞表面所必需的。这个11.6kb区域包含一个编码60千达尔顿蛋白的基因kpsD。 kpsD基因位于一个2.4kb PstI-BamHI片段上。在kpsD中包含Tn1000插入的细胞无法合成60千达蛋白，并且不会在细胞表面表达多糖。然而，细胞提取物的免疫扩散和火箭免疫电泳表明，K1多糖是由这些细胞合成的。我们提供的证据表明，kpsD基因产物是作为前体合成的，加工后的形式位于周质空间中。 kpsD-phoA融合蛋白的碱性磷酸酶活性分析表明，kpsD表达处于正调控状态。使用位于kpsD编码序列内的260个碱基对的AluI片段作为探针，发现该片段可与大肠杆菌的染色体DNA杂交，该DNA合成K2，K5，K7，K12和K13荚膜多糖，但不合成K3和K100。这些结果表明，不仅要输出K1，而且还需要其他K抗原，可能都需要kpsD基因产物。

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