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首页> 外文期刊>Infection and immunity >Nucleotide sequence of the lecithinase operon of Listeria monocytogenes and possible role of lecithinase in cell-to-cell spread.
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Nucleotide sequence of the lecithinase operon of Listeria monocytogenes and possible role of lecithinase in cell-to-cell spread.

机译：单核细胞增多性李斯特菌卵磷脂酶操纵子的核苷酸序列以及卵磷脂酶在细胞间传播中的可能作用。

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The lecithinase gene of the intracellular pathogen Listeria monocytogenes, plcB, was identified in a 5,648-bp DNA fragment which expressed lecithinase activity when cloned into Escherichia coli. This fragment is located immediately downstream of the previously identified gene mpl (prtA). It contains five open reading frames, named actA, plcB, and ORFX, -Y, and -Z, which, together with mpl, form an operon, since a 5.7-kb-long transcript originates from a promoter located upstream of mpl (J. Mengaud, C. Geoffroy, and P. Cossart, Infect. Immun. 59:1043-1049, 1991). A second promoter was detected in front of actA which encodes a putative membrane protein containing a region of internal repeats. plcB encodes the lecithinase, a predicted 289-amino-acid protein homologous to the phosphatidylcholine-specific phospholipases C of Bacillus cereus and Clostridium perfringens (alpha-toxin). plcB mutants produce only small plaques on fibroblast monolayers, and an electron microscopic analysis of infected macrophages suggests that lecithinase is involved in the lysis of the two-membrane vacuoles that surround the bacteria after cell-to-cell spread. On the opposite DNA strand, downstream of the operon, three more open reading frames, ldh, ORFA, and ORFB, were found. The deduced amino acid sequence of the first one is homologous to lactate dehydrogenases. Low-stringency Southern hybridization experiments suggest that these three open reading frames lie outside of the L. monocytogenes virulence region: mpl and actA were specific for L. monocytogenes, sequences hybridizing to plcB were detected in L. ivanovii and L. seeligeri, and sequences hybridizing to ORFX, -Y, and -Z were found in L. innocua. In contrast to this, sequences hybridizing to ldh or ORFB were detected in all Listeria species (including the nonpathogenic ones).
机译：在一个5,648-bp的DNA片段中鉴定出了胞内病原体单核细胞增生性李斯特菌的卵磷脂酶基因plcB，该DNA片段在克隆到大肠杆菌中时可表达卵磷脂酶活性。该片段位于先前鉴定的基因mpl（prtA）的下游。它包含五个开放阅读框，分别命名为actA，plcB和ORFX，-Y和-Z，它们与mpl一起形成操纵子，因为一个5.7 KB长的转录本来自位于mpl上游的启动子（J Mengaud，C.Geoffroy和P.Cossart，Infect.Immun.59：1043-1049，1991）。在actA前面检测到第二个启动子，该启动子编码包含内部重复区域的推定膜蛋白。 plcB编码卵磷脂酶，卵磷脂是一种预测的289个氨基酸蛋白，与蜡状芽孢杆菌和产气荚膜梭菌的磷脂酰胆碱特异性磷脂酶C同源。 plcB突变体在成纤维细胞单层上仅产生小噬菌斑，并且对感染的巨噬细胞进行电子显微镜分析表明，卵磷脂酶参与了细胞间扩散后围绕细菌的两膜液泡的裂解。在操纵子下游的另一条DNA链上，发现了另外三个开放阅读框ldh，ORFA和ORFB。推导的第一个氨基酸序列与乳酸脱氢酶同源。低严格性Southern杂交实验表明，这三个开放阅读框位于单核细胞增生李斯特菌毒力区域之外：mpl和actA对单核细胞增生李斯特菌具有特异性，在伊万诺维菌和Seeligeri乳杆菌中检测到与plcB杂交的序列，以及序列在无毒乳杆菌中发现与ORFX杂交的-Y和-Z。与此相反，在所有李斯特菌属物种（包括非致病性物种）中均检测到了与ldh或ORFB杂交的序列。

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