The T4 RI antiholin has an N-terminal signal anchor release domain that targets it for degradation by DegP
The T4 RI antiholin has an N-terminal signal anchor release domain that targets it for degradation by DegP
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DOI：
10.1128/jb.00854-07
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发表时间：
2007-11-01
影响因子：
3.2
通讯作者：
Young, Ry
中科院分区：
文献类型：
--
作者：
Tran, Tram Anh T.;Struck, Douglas K.;Young, Ry
t4感染细胞的裂解抑制（LIN）是现代分子遗传学的基础实验系统之一。在LIN中，t4感染细胞的继发性感染导致感染周期显著延长，其中细胞内噬菌体和内溶素积累可持续数小时。在分子水平上，这是由于holin T被抗holin RI抑制所致。RI只有97个残基，包含一个n端疏水结构域和一个c端亲水结构域；后一结构域融合到分泌信号序列的表达，由于其与T holin的质周结构域的特异性相互作用，足以施加LIN。在这里，我们发现n端序列包含一个信号锚点释放（SAR）结构域，该结构域导致RI以膜系链形式分泌，然后随后释放到外周质中，没有蛋白水解过程。此外，尽管LIN在degP宿主中不受影响，但SAR结构域在RI的释放形式上赋予功能稳定性和degP介导的蛋白水解不稳定性。这些结果讨论了一个模型的激活RI在建立LIN状态。
Lysis inhibition (LIN) of T4-infected cells was one of the foundational experimental systems for modern molecular genetics. In LIN, secondary infection of T4-infected cells results in a dramatically protracted infection cycle in which intracellular phage and endolysin accumulation can continue for hours. At the molecular level, this is due to the inhibition of the holin, T, by the antiholin, RI. RI is only 97 residues and contains an N-terminal hydrophobic domain and a C-terminal hydrophilic domain; expression of the latter domain fused to a secretory signal sequence is sufficient to impose LIN, due to its specific interaction with the periplasmic domain of the T holin. Here we show that the N-terminal sequence comprises a signal anchor release (SAR) domain, which causes the secretion of RI in a membrane-tethered form and then its subsequent release into the periplasm, without proteolytic processing. Moreover, the SAR domain confers both functional lability and DegP-mediated proteolytic instability on the released form of RI, although LIN is not affected in a degP host. These results are discussed in terms of a model for the activation of RI in the establishment of the LIN state.