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首页> 外文期刊>Journal of Molecular Biology >Molecular Basis for Immunity Protein Recognition of a Type VII Secretion System Exported Antibacterial Toxin
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Molecular Basis for Immunity Protein Recognition of a Type VII Secretion System Exported Antibacterial Toxin

机译：抗免疫蛋白质识别的分子基础，VII分泌系统出口抗菌毒素

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摘要

Gram-positive bacteria deploy the type VII secretion system (T7SS) to facilitate interactions between eukaryotic and prokaryotic cells. In recent work, we identified the TelC protein fromStreptococcus intermediusas a T7SS-exported lipid II phosphatase that mediates interbacterial competition. TelC exerts toxicity in the inner wall zone of Gram-positive bacteria; however, intercellular intoxication of sister cells does not occur because they express the TipC immunity protein. In the present study, we sought to characterize the molecular basis of self-protection by TipC. Using sub-cellular localization and protease protection assays, we show that TipC is a membrane protein with an N-terminal transmembrane segment and a C-terminal TelC-inhibitory domain that protrudes into the inner wall zone. The 1.9-? X-ray crystal structure of a non-protective TipC paralogue reveals that the soluble domain of TipC proteins adopts a crescent-shaped fold that is composed of three α-helices and a seven-stranded β-sheet. Subsequent homology-guided mutagenesis demonstrates that a concave surface formed by the predicted β-sheet of TipC is required for both its interaction with TelC and its TelC-inhibitory activity.S. intermediuscells lacking thetipCgene are susceptible to growth inhibition by TelC delivered between cells; however, we find that the growth of this strain is unaffected by endogenous or overexpressed TelC, although the toxin accumulates in culture supernatants. Together, these data indicate that the TelC-inhibitory activity of TipC is only required for intercellularly transferred TelC and that the T7SS apparatus transports TelC across the cell envelope in a single step, bypassing the cellular compartment in which it exerts toxicity en route.
机译：革兰氏阳性细菌部署VII分泌系统（T7S），以促进真核和原核细胞之间的相互作用。在最近的工作中，我们鉴定了Impertearcocccus的TELC蛋白，其T7SS-出口的脂质II磷酸酶介导区间竞争。 Telc在革兰氏阳性细菌的内壁区施加毒性;然而，由于它们表达钛酸免疫蛋白，因此不会出现细胞间中毒。在本研究中，我们寻求对Tipc进行自我保护的分子基础。使用亚细胞定位和蛋白酶保护测定，我们表明TIPC是具有N-末端跨膜段的膜蛋白和突出到内壁区的C末端电信抑制域。 1.9-？非保护钛蛋白酶的X射线晶体结构表明，Tipc蛋白的可溶性结构域采用新月形折叠，该折叠由三个α-螺旋和七链β-薄片组成。随后的同源引导诱变证明其通过预测β-片材形成的凹面是与TELC的相互作用及其TELC抑制活性所必需的。缺乏Thetipcgene的含水蛋白细胞易受细胞中递送的Telc生长抑制的影响;然而，我们发现这种菌株的生长不受内源性或过表达的Telc影响，尽管毒素在培养上清液中积聚。这些数据表明，巧妙的TIPC的TELC抑制活性仅适用于细胞间转移的电信，并且T7SS装置在单个步骤中通过细胞包络传输TELC，绕过其施加毒性的蜂窝室。

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