In Gram-negative bacteria, secretion of toxins ensure the survival of the bacterium. Such toxins are secreted by sophisticated multiprotein systems. The most conserved part in some of these secretion systems are components, called secretins, which form the outer membrane ring in these systems. Recent structural studies shed some light on the oligomeric organization of secretins. However, the mechanisms by which these proteins are targeted to the outer membrane and assemble there into ring structures are still not fully understood. This review discusses the various species-specific targeting and assembly pathways that are taken by secretins in order to form their functional oligomers.

在革兰氏阴性细菌中，毒素的分泌可确保细菌的生存。这种毒素是由复杂的多蛋白系统分泌的。在这些分泌系统中，最保守的部分是称为分泌素的成分，它们在这些系统中形成外膜环。最近的结构研究为促胰液素的低聚结构提供了一些启示。然而，这些蛋白质靶向外膜并在那里组装成环结构的机制仍不完全清楚。这篇综述讨论了促胰液素形成其功能性寡聚体所采取的各种物种特异性靶向和组装途径。