The Spanin Complex Is Essential for Lambda Lysis
The Spanin Complex Is Essential for Lambda Lysis
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DOI：
10.1128/jb.01245-12
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发表时间：
2012-10-01
影响因子：
3.2
通讯作者：
Young, Ry
中科院分区：
文献类型：
--
作者：
Berry, Joel;Rajaure, Manoj;Young, Ry
噬菌体裂解是一种普遍存在的生物过程，是生物圈中最常见的细胞杀伤事件。革兰氏阴性宿主的裂解已显示需要孔蛋白和内溶素，其分别攻击细胞质膜和肽聚糖。最近，第三类裂解蛋白，spanins，被确定。第一个spanins的特点是λ Rz和Rz 1，一个完整的细胞质膜蛋白和外膜脂蛋白，分别。先前的工作表明，Rz和Rz 1形成跨越整个周质的复合物。相差视频显微镜用于记录诱导的λ溶原细胞携带前噬菌体的裂解所涉及的形态学变化，所述前噬菌体具有λ典型孔蛋白-内溶素系统或噬菌体21针孔蛋白-信号锚释放（SAR）内溶素系统。在前者，杆形态持续到瞬间的爆炸性极破裂，立即清空其内容物的细胞。相比之下，在针孔蛋白-SAR内溶素裂解中，细胞开始变短并均匀地变短，最终产生的圆形细胞破裂。在这两种情况下，裂解未能发生在诱导携带无效突变的spanin基因的同基因原噬菌体。在这两个系统中，而不是一个信封破裂，诱导细胞从一个棒形转化为一个球形的形式。一个功能性的GFP Phi Rz嵌合体被证明表现出点状分布时，共表达Rz 1，尽管缺乏内溶素功能。提出了一种模型，其中spanins进行破坏外膜的基本步骤，以调节的方式由肽聚糖层的状态。
Phage lysis is a ubiquitous biological process, the most frequent cytocidal event in the biosphere. Lysis of Gram-negative hosts has been shown to require holins and endolysins, which attack the cytoplasmic membrane and peptidoglycan, respectively. Recently, a third class of lysis proteins, the spanins, was identified. The first spanins to be characterized were lambda Rz and Rz1, an integral cytoplasmic membrane protein and an outer membrane lipoprotein, respectively. Previous work has shown that Rz and Rz1 form complexes that span the entire periplasm. Phase-contrast video microscopy was used to record the morphological changes involved in the lysis of induced lambda lysogens carrying prophages with either the lambda canonical holin-endolysin system or the phage 21 pinholin-signal anchor release (SAR) endolysin system. In the former, rod morphology persisted until the instant of an explosive polar rupture, immediately emptying the cell of its contents. In contrast, in pinholin-SAR endolysin lysis, the cell began to shorten and thicken uniformly, with the resultant rounded cell finally bursting. In both cases, lysis failed to occur in inductions of isogenic prophages carrying null mutations in the spanin genes. In both systems, instead of an envelope rupture, the induced cells were converted from a rod shape to a spherical form. A functional GFP Phi Rz chimera was shown to exhibit a punctate distribution when coexpressed with Rz1, despite the absence of endolysin function. A model is proposed in which the spanins carry out the essential step of disrupting the outer membrane, in a manner regulated by the state of the peptidoglycan layer.