RfaH enhances elongation of Escherichia coli hlyCABD mRNA
RfaH enhances elongation of Escherichia coli hlyCABD mRNA
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DOI：
10.1128/jb.178.7.1850-1857.1996
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发表时间：
1996-04-01
影响因子：
3.2
通讯作者：
Welch, RA
中科院分区：
文献类型：
--
作者：
Leeds, JA;Welch, RA
大肠杆菌hlyCABD操纵子编码细胞外溶细胞毒素的多肽组分（HlyA），以及其酰化（HlyC）和sec非依赖性分泌（HlyBD）所需的蛋白质。以前的报道认为，E.大肠杆菌蛋白RfaH是野生型溶血素表达所必需的，或者通过正激活hly转录起始（M. J. A. Bailey，V. Koronakis，T. Schmoll，和C.休斯，摩尔。Microbiol. 6：1003-1012，1992）或通过促进溶血素输出机制在E. coli外膜（C. Wandersman和S.勒托夫Microbiol，7：141-150，1993）。从rfaQ-K、traY-Z和rplK-rpoC基因簇中的启动子远端基因转录的mRNA的野生型水平也需要RfaH，这表明RfaH是转录抗终止子。我们通过分析rfaH突变对hlyCABD mRNA合成和降解、HlyA蛋白水平和溶血活性的影响来测试这些模型。coli和E.结果表明，RfaH能增强hlyCABD转录本的延伸，这与RfaH参与大肠杆菌中hlyCABD转录反终止的模型一致。杆菌我们还证明了RfaH增加毒素功效。溶血素活性的调节可能是RfaH依赖性E.大肠杆菌外膜化学型，这与溶血活性中的脂多糖参与的模型一致。
Escherichia coli hlyCABD operons encode the polypeptide component (HlyA) of an extracellular cytolytic toxin, as well as proteins required for its acylation (HlyC) and sec-independent secretion (HlyBD). Previous reports suggested that the E. coli protein RfaH is required for wild-type hemolysin expression, either by positively activating hly transcript initiation (M. J. A. Bailey, V. Koronakis, T. Schmoll, and C. Hughes, Mol. Microbiol. 6:1003-1012, 1992) or by promoting proper insertion of hemolysin export machinery in the E. coli outer membrane (C. Wandersman and S. Letoffe, Mol. Microbiol, 7:141-150, 1993). RfaH is also required for wild-type levels of mRNA transcribed from promoter-distal genes in the rfaQ-K, traY-Z, and rplK-rpoC gene clusters, suggesting that RfaH Is a transcriptional antiterminator. We tested these models by analyzing the effects of rfaH mutations on hlyCABD mRNA synthesis and decay, HlyA protein levels, and hemolytic activity, The model system included a uropathogenic strain of E. coli harboring hlyCABD on the chromosome and E. coli K-12 transformed with the hlyCABD operon on a recombinant plasmid, Our results suggest that RfaH enhances hlyCABD transcript elongation, consistent with the model of RfaH involvement in transcriptional antitermination in E. coli. We also demonstrated that RfaH increases toxin efficacy. Modulation of hemolysin activity may be an indirect effect of RfaH-dependent E. coli outer membrane chemotype, which is consistent with the model of lipopolysaccharide involvement in hemolytic activity.