Desvaux Mickaël, Cooper Lisa M, Filenko Nina A, Scott-Tucker Anthony, Turner Sue M, Cole Jeffrey A, Henderson Ian R
Division of Immunity and Infection, The University of Birmingham, Edgbaston, Birmingham, UK.
FEMS Microbiol Lett. 2006 Nov;264(1):22-30. doi: 10.1111/j.1574-6968.2006.00425.x.
The plasmid encoded toxin, Pet, is a prototypical member of the serine protease autotransporters of the Enterobacteriaceae. In addition to the passenger and beta-domains typical of autotransporters, in silico predictions indicate that Pet possesses an unusually long N-terminal signal sequence. The signal sequence can be divided into five regions termed N1 (charged), H1 (hydrophobic), N2, H2 and C (cleavage site) domains. The N1 and H1 regions, which we have termed the extended signal peptide region, demonstrate remarkable conservation. In contrast, the N2, H2 and C regions demonstrate significant variability and are reminiscent of typical Sec-dependent signal sequences. Despite several investigations, the function of the extended signal peptide region remains obscure and surprisingly it has not been proven that the extended signal peptide region is actually synthesized as part of the signal sequence. Here, we demonstrate that the extended signal peptide region is present only in Gram-negative bacterial proteins originating from the classes Beta- and Gammaproteobacteria, and more particularly only in proteins secreted via the Type V secretion pathway: autotransporters, TpsA exoproteins of the two-partner system and trimeric autotransporters. In vitro approaches demonstrate that the DNA region encoding the extended signal peptide region is transcribed and translated.
质粒编码的毒素Pet是肠杆菌科丝氨酸蛋白酶自转运蛋白的典型成员。除了自转运蛋白典型的乘客结构域和β结构域外，计算机预测表明Pet拥有异常长的N端信号序列。该信号序列可分为五个区域，称为N1（带电荷）、H1（疏水）、N2、H2和C（切割位点）结构域。我们将N1和H1区域称为延伸信号肽区域，它们表现出显著的保守性。相比之下，N2、H2和C区域表现出显著的变异性，让人联想到典型的依赖Sec的信号序列。尽管进行了多项研究，但延伸信号肽区域的功能仍然不清楚，令人惊讶的是，尚未证实延伸信号肽区域实际上是作为信号序列的一部分合成的。在这里，我们证明延伸信号肽区域仅存在于源自β-和γ-变形菌纲的革兰氏阴性细菌蛋白中，更特别的是仅存在于通过V型分泌途径分泌的蛋白中：自转运蛋白、双组分系统的TpsA外蛋白和三聚体自转运蛋白。体外实验表明，编码延伸信号肽区域的DNA区域被转录和翻译。
