Bubert A, Kestler H, Götz M, Böckmann R, Goebel W
Theodor-Boveri-Institut für Biowissenschaften, Lehrstuhl für Mikrobiologie, Universität Würzburg, Germany.
Mol Gen Genet. 1997 Sep;256(1):54-62. doi: 10.1007/s004380050545.
The iap gene of Listeria monocytogenes encodes the extracellular protein p60, which possesses a murein hydrolase activity necessary for septum separation. We constructed L. monocytogenes EGD strains harbouring plasmids that carry the iap gene under the control of the PrfA-regulated promoters of the L. monocytogenes genes hly, mpl, and actA. After insertional inactivation of the chromosomal iap gene in L. monocytogenes EGD, p60 synthesis was strictly dependent on PrfA. Elevated temperature (40 degrees C) enhanced synthesis of p60 in L. monocytogenes when the iap gene was under the control of the hly promoter; this appeared to be associated with increased synthesis of PrfA at this temperature. Synthesis of p60 in L. monocytogenes was significantly lower when the iap gene was placed under the control of the actA or the mpl promoter. Transcription of the iap gene was repressed in L. monocytogenes in the presence of PrfA when iap expression was under the control of the prfA promoter P2. Under the control of the hly promoter the gene produced low levels of secreted p60 in the presence of low amounts of PrfA, and this in turn led to the generation of long listerial cell filaments consisting of bacteria that had failed to separate. Overexpression of p60 in the presence of high levels of PrfA caused formation of single cells, which showed reduced viability depending on the level of secreted p60. These data suggest that the iap gene may be a valuable tool for monitoring virulence gene regulation by PrfA under in vivo conditions, without disturbing the integrity of the infected host cells.
单核细胞增生李斯特菌的iap基因编码细胞外蛋白p60，该蛋白具有隔膜分离所必需的胞壁质水解酶活性。我们构建了携带在单核细胞增生李斯特菌基因hly、mpl和actA的PrfA调控启动子控制下的iap基因的质粒的单核细胞增生李斯特菌EGD菌株。在单核细胞增生李斯特菌EGD中染色体iap基因插入失活后，p60的合成严格依赖于PrfA。当iap基因在hly启动子控制下时，升高温度（40℃）可增强单核细胞增生李斯特菌中p60的合成；这似乎与该温度下PrfA合成增加有关。当iap基因置于actA或mpl启动子控制下时，单核细胞增生李斯特菌中p60的合成显著降低。当iap表达受prfA启动子P2控制时，在存在PrfA的情况下，单核细胞增生李斯特菌中iap基因的转录受到抑制。在hly启动子控制下，该基因在低水平PrfA存在时产生低水平的分泌型p60，这反过来导致由未能分离的细菌组成的长李斯特菌细胞丝的产生。在高水平PrfA存在下p60的过表达导致单细胞形成，其活力根据分泌的p60水平而降低。这些数据表明，iap基因可能是监测体内条件下PrfA对毒力基因调控的有价值工具，而不会干扰受感染宿主细胞的完整性。
