Transmembrane substrates of type three secretion system injectisomes

The type three secretion system injectisome of Gram-negative bacterial pathogens injects virulence proteins, called effectors, into host cells. Effectors of mammalian pathogens carry out a range of functions enabling bacterial invasion, replication, immune suppression and transmission. The injectisome secretes two translocon proteins that insert into host cell membranes to form a translocon pore, through which effectors are delivered. A subset of effectors also integrate into infected cell membranes, enabling a unique range of biochemical functions. Both translocon proteins and transmembrane effectors avoid cytoplasmic aggregation and integration into the bacterial inner membrane. Translocated transmembrane effectors locate and integrate into the appropriate host membrane. In this review, we focus on transmembrane translocon proteins and effectors of bacterial pathogens of mammals. We discuss what is known about the mechanisms underlying their membrane integration, as well as the functions conferred by the position of injectisome effectors within membranes.

Automated summary

The injectisome of Gram-negative bacterial pathogens injects virulence proteins into host cells, enabling invasion, replication, immune suppression, and transmission. This system secretes translocon proteins that form a pore in host cell membranes, allowing the delivery of effectors. Some effectors integrate into infected cell membranes, providing unique biochemical functions. This review focuses on the membrane integration mechanisms and functions of translocon proteins and effectors in mammalian bacterial pathogens.