Frey J, Beck M, Stucki U, Nicolet J
Institute for Veterinary Bacteriology, University of Berne, Switzerland.
Gene. 1993 Jan 15;123(1):51-8. doi: 10.1016/0378-1119(93)90538-e.
Among the twelve different serotypes of Actinobacillus pleuropneumoniae, the causative agent of swine pleuropneumonia, a strongly active hemolysin I (HlyI) is produced by serotypes which are particularly virulent, and less active hemolysin II (HlyII) is produced by all serotypes except type 10. In the serotypes 1, 5a, 5b, 9, 10 and 11, which produce HlyI, the hemolysin (hly) operon consists of a structural hlyIA gene, encoding pre-HlyI, an activator gene, hlyIC, necessary for the activation of pre-Hly to active Hly, and two genes, hlyIB and hlyID, involved in Hly secretion. These genes are clustered in the order, hlyICABD. This is characteristic to RTX toxin (repeats in the structural toxin) operons. The HlyII operons in all serotypes producing HlyII consist only of the pre-HlyII-encoding gene, appA, and its activator gene, appC. The serotypes, which produce HlyII, but not HlyI, contain a truncated HlyI operon, with the promoter, hlyIB and hlyID, and a small segment of the C terminus of hlyIA. This partial HlyI operon might have been formed by deletion of hlyIC and most of hlyIA. In serotype 3, which produces HlyII, but no HlyI, and which releases only minute amounts of this Hly into the growth medium, none of the hlyI genes and consequently no Hly secretion genes were found. The above results postulate that HlyII is secreted via the products of hlyIB and hlyID, and explain the low amount of HlyII secreted by serotype 3. Cloning and analysis of the structural genes encoding pre-HlyI and pre-HlyII among the different serotypes revealed differences in the hlyIA genes which are highly similar in the serologically related serotypes 1, 9 and 11, and differ from the serotypes, 5a, 5b and 10. The hlyIIA genes, in contrast, seem to be conserved in all serotypes.
在猪胸膜肺炎的病原体胸膜肺炎放线杆菌的12种不同血清型中，特别具有毒力的血清型产生强活性溶血素I（HlyI），除10型外的所有血清型产生活性较弱的溶血素II（HlyII）。在产生HlyI的1、5a、5b、9、10和11型血清型中，溶血素（hly）操纵子由编码前HlyI的结构hlyIA基因、激活前Hly转化为活性Hly所必需的激活基因hlyIC以及参与Hly分泌的两个基因hlyIB和hlyID组成。这些基因按hlyICABD的顺序聚集。这是RTX毒素（结构毒素中的重复序列）操纵子的特征。所有产生HlyII的血清型中的HlyII操纵子仅由编码前HlyII的基因appA及其激活基因appC组成。产生HlyII但不产生HlyI的血清型含有截短的HlyI操纵子，带有启动子、hlyIB和hlyID以及hlyIA C末端一小段。这个部分HlyI操纵子可能是由hlyIC和大部分hlyIA的缺失形成的。在产生HlyII但不产生HlyI且仅向生长培养基中释放微量该Hly的3型血清型中，未发现任何hlyI基因，因此也未发现Hly分泌基因。上述结果推测HlyII是通过hlyIB和hlyID的产物分泌的，并解释了3型血清型分泌的HlyII量较低的原因。对不同血清型中编码前HlyI和前HlyII的结构基因进行克隆和分析发现，hlyIA基因存在差异，在血清学相关的1、9和11型血清型中高度相似，与5a、5b和10型血清型不同。相比之下，hlyIIA基因似乎在所有血清型中都保守。
