Identification of a target cell permissive factor required for contact-dependent growth inhibition (CDI)
Identification of a target cell permissive factor required for contact-dependent growth inhibition (CDI)
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DOI：
10.1101/gad.182345.111
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发表时间：
2012-03-01
影响因子：
10.5
通讯作者：
Hayes, Christopher S.
中科院分区：
文献类型：
--
作者：
Diner, Elie J.;Beck, Christina M.;Hayes, Christopher S.
细菌接触依赖性生长抑制（CDI）是由CdiB/CdiA家族的双伴侣分泌蛋白介导的。CdiA效应蛋白被输出到CDI+抑制剂细胞的表面上，在那里它们与易感细菌相互作用并递送源自其C-末端区域的效应物/毒素（CdiA-CT）。CDI+细胞还产生结合CdiA-CT并阻断其活性以防止自身抑制的免疫蛋白。在这里，我们表明，从尿路致病性大肠杆菌菌株536（UPEC 536）的CdiA-CT是一个潜在的tRNase，需要激活的生物合成酶CysK（O-乙酰丝氨酸硫化氢解酶A）。UPEC 536 CdiA-CT在体外不表现出核酸酶活性，但当加入纯化的CysK时，在转移RNA（tRNA）反密码子环内切割。CysK和CdiA-CT形成稳定的复合物，并且它们的结合相互作用似乎模拟CysK/CysE半胱氨酸合酶复合物的结合相互作用。生长抑制也需要CdiA-CT激活。在E. coli cysK（+）细胞抑制细胞生长，而Delta cysK突变体的生长不受毒素的影响。此外，E. coli Delta cysK细胞对表达UPEC 536 CdiA的抑制剂细胞完全耐受，表明在CDI期间需要CysK来激活tRNase。因此，CysK作为CDI的容许因子，提供了调节靶细胞中生长抑制的潜在机制。
Bacterial contact-dependent growth inhibition (CDI) is mediated by the CdiB/CdiA family of two-partner secretion proteins. CdiA effector proteins are exported onto the surface of CDI+ inhibitor cells, where they interact with susceptible bacteria and deliver effectors/toxins derived from their C-terminal regions (CdiA-CT). CDI+ cells also produce an immunity protein that binds the CdiA-CT and blocks its activity to prevent autoinhibition. Here, we show that the CdiA-CT from uropathogenic Escherichia coli strain 536 (UPEC536) is a latent tRNase that requires activation by the biosynthetic enzyme CysK (O-acetylserine sulfhydrylase A). UPEC536 CdiA-CT exhibits no nuclease activity in vitro, but cleaves within transfer RNA (tRNA) anti-codon loops when purified CysK is added. CysK and CdiA-CT form a stable complex, and their binding interaction appears to mimic that of the CysK/CysE cysteine synthase complex. CdiA-CT activation is also required for growth inhibition. Synthesis of CdiA-CT in E. coli cysK(+) cells arrests cell growth, whereas the growth of Delta cysK mutants is unaffected by the toxin. Moreover, E. coli Delta cysK cells are completely resistant to inhibitor cells expressing UPEC536 CdiA, indicating that CysK is required to activate the tRNase during CDI. Thus, CysK acts as a permissive factor for CDI, providing a potential mechanism to modulate growth inhibition in target cells.