Actinobacillus pleuropneumoniae hlyX gene homology with the fnr gene of Escherichia coli
Actinobacillus pleuropneumoniae hlyX gene homology with the fnr gene of Escherichia coli
复制标题
胸膜肺炎放线杆菌 hlyX 基因与大肠杆菌 fnr 基因同源性
作者：
J. MacInnes;J. E. Kim;C. Lian;G. Soltes
对胸膜肺炎放线杆菌的hlyX基因进行了序列测定，并对其在基因表达调控中的作用进行了研究。HlyX序列与已知的溶血素或细胞毒素基因序列没有相似性。然而，hlyX序列与编码全球调控蛋白FNR的大肠杆菌的FNR基因非常相似。HlyX基因产物(HlyX)的推导氨基酸序列与FNR的氨基酸序列比较表明，整个多肽链具有高度的序列相关性。例如，在FNR的DNA结合区的24个氨基酸中，有23个在HlyX的相应区域是相同的。氨基末端的四个半胱氨酸残基也是保守的。HlyX的启动子区域与FNR非常相似。它有一个推定的-10序列，与E.Coli-10的共识序列非常相似。该序列被一个潜在的操纵子重叠，该操纵子与FNR结合位点共识序列非常相似。HlyX和FNR的功能同源性也被证明。携带hlyX的质粒补充了FNR缺失菌株的营养损伤。这些数据表明，HlyX可能调节而不是调节大肠杆菌中的溶血活性，但不能排除HlyX既是基因表达的调节者又是溶血素的可能性。
The hlyX gene from Actinobacillus pleuropneumoniae, which confers a hemolytic phenotype on Escherichia coli, was sequenced, and its role in regulation of gene expression was investigated. No similarity was found between the hlyX sequence and sequences of known hemolysin or cytotoxin genes. However, the hlyX sequence was very similar to that of the fnr gene of Escherichia coli which encodes the global regulatory protein, FNR. Comparison of the deduced amino acid sequence of the hlyX gene product (HlyX) with that of FNR revealed a high degree of well-aligned sequence correlation throughout the polypeptide chain. For example, 23 of 24 amino acids in the DNA-binding region of FNR are identical in the corresponding region of HlyX. Four cysteine residues in the amino-terminal region are also conserved. The promoter region of hlyX is very similar to that of fnr. It has a putative -10 sequence which closely resembles the E. coli -10 consensus sequence. This sequence is overlapped by a potential operator which is very similar to the FNR-binding-site consensus sequence. Functional homology between HlyX and FNR was also demonstrated. Plasmids carrying hlyX complemented the nutritional lesion of an fnr deletion strain of E. coli. These data suggest that HlyX may regulate, rather than mediate, hemolytic activity in E. coli, but the possibility that HlyX is both a regulator of gene expression and a hemolysin cannot be excluded.