Type V Secretion Systems in Bacteria

Abstract

Type V secretion denotes a variety of secretion systems that cross the outer membrane in Gram-negative bacteria but that depend on the Sec machinery for transport through the inner membrane. They are possibly the simplest bacterial secretion systems, because they consist only of a single polypeptide chain (or two chains in the case of two-partner secretion). Their seemingly autonomous transport through the outer membrane has led to the term "autotransporters" for various subclasses of type V secretion. In this chapter, we review the structure and function of these transporters and review recent findings on additional factors involved in the secretion process, which have put the term "autotransporter" to debate.

Two-Partner Secretion: Combining Efficiency and Simplicity in the Secretion of Large Proteins for Bacteria-Host and Bacteria-Bacteria Interactions

“…The observation that a disordered, negatively charged polypeptide can be secreted thus suggests that an electrochemical potential based on large, impermeable charged molecules may indeed be present across the bacterial OM and play a role in type V secretion. In addition, the process might also benefit from entropic effects due to the difference between the crowded periplasmic environment and the extracellular milieu (Fan et al, 2016); however, extracellular crowding agents have not been observed to affect AT secretion (Drobnak et al, 2015). …”

“…They are homotrimers whose passenger domains assemble into long, rather rigid stalks with a “head,” and harbor domains rich in β structure interspersed with helical coiled coils (reviewed in Fan et al, 2016). Each monomer contributes its four C-terminal β strands to the pore-forming transmembrane β barrel (Leo et al, 2012).…”

“…We will cover the structural and mechanistic aspects of the TPS pathway, and to do so we will compare with other Type V systems where relevant. Earlier work will only be mentioned briefly, and thus readers are referred to previous reviews for more details (Jacob-Dubuisson et al, 2013; van Ulsen et al, 2014; Fan et al, 2016). …”

The invasin D protein from Yersinia pseudotuberculosis selectively binds the Fab region of host antibodies and affects colonization of the intestine

“…Ail is furthermore required for full virulence of Y. pestis and the delivery of pathogenicity factors into host cells (9)(10)(11)(12). The invasin subfamily comprises adhesins of the inverse autotransporter group also referred to as type Ve secretion system (13,14). InvA represents the prototype of the large bacterial invasin subfamily of adhesins (reviewed in (2,3,13)).…”

Super-Resolution Imaging of Protein Secretion Systems and the Cell Surface of Gram-Negative Bacteria

“…Because these systems are detailed elsewhere in this special edition, we have focused our review on studies where spatial distribution appears to be important either to the biogenesis of the secretion system, or to its function. As highlighted in Figure 2, the architecture of these secretion nanomachines can differ from single component systems, to relatively simple systems composed of only 3 subunits, to multicomponent systems containing over 20 protein subunits and spanning all four compartments of the bacterial cell (Dalbey and Kuhn, 2012; Campos et al, 2013; Galán et al, 2014; Ho et al, 2014; Thomas et al, 2014; Trokter et al, 2014; van Ulsen et al, 2014; Zoued et al, 2014; Basler, 2015; Costa et al, 2015; Fan et al, 2016; Notti and Stebbins, 2016). …”