Emerging themes in SecA2-mediated protein export

The conserved general secretion (Sec) pathway carries out most protein export in bacteria and is powered by the essential SecA ATPase. Interestingly, mycobacteria and some Gram positive bacteria possess two SecA proteins: SecA1 and SecA2. In these species, SecA1 is responsible for exporting the majority of proteins whereas SecA2 exports only a subset of substrates and is implicated in virulence. However, despite the impressive body of knowledge on the canonical SecA (SecA1), less is known concerning SecA2 function. Here, we review our current understanding of the different types of SecA2 systems and outline future directions for SecA2 studies