The two-partner secretion pathway in Gram-negative bacteria

我们的研究重点是之前在大肠杆菌基因组注释中描述的TPS系统。coliO 157：H7菌株EDL 933。 我们指定该系统的外蛋白和转运蛋白组分OtpA和OtpB，分别。 我们发现，OtpA和OtpB不属于TPS系统的两个主要亚型（溶血素和粘附素）的基础上，他们的序列预测。 然而，我们获得了直接的证据，OtpA和OtpB构成了一个真正的双伴侣分泌系统。 我们发现在E. coli O 157：H7需要OtpB，而OtpA在大肠杆菌中产生时需要OtpB。coliK-12菌株，其分泌严格依赖于OtpB的产生。 此外，我们已经使用OtpA/OtpB作为模型系统来表征通过TPS途径的分泌动力学。 尽管外蛋白在被挤出到细胞外空间之前必须靶向转运蛋白，但我们发现通过TPS途径的蛋白分泌非常迅速。 最近，我们一直在使用OtpA/OtpB系统，以了解外蛋白分泌的机制。最值得注意的是，我们已经获得了强有力的证据表明，OtpA是跨内膜和外膜运输在两个连续的步骤。

Our studies have focused on a TPS system that was previously described in the annotation of the genome of E. coli O157:H7 strain EDL933. We designated the exoprotein and transporter components of this system OtpA and OtpB, respectively. We found that OtpA and OtpB are not predicted to belong to either of the two major subtypes of TPS systems (hemolysins and adhesins) based on their sequence. Nevertheless, we obtained direct evidence that OtpA and OtpB constitute a bona fide two-partner secretion system. We found that secretion of OtpA into the extracellular environment in E. coli O157:H7 requires OtpB and that when OtpA is produced in an E. coli K-12 strain, its secretion is strictly dependent on the production of OtpB. Furthermore, we have used OtpA/OtpB as a model system to characterize the kinetics of secretion via the TPS pathway. Despite the fact that the exoprotein must be targeted to the transporter before it is extruded into the extracellular space, we found that protein secretion via the TPS pathway is extremely rapid. Recently, we have been using the OtpA/OtpB system to gain insight into the mechanism of exoprotein secretion. Most notably, we have obtained strong evidence that OtpA is transported across the inner and outer membranes in two sequential steps.