Structure and function of minor pilins of type IV pili

Abstract

Type IV pili are versatile and highly flexible fibers formed on the surface of many Gram-negative and Gram-positive bacteria. Virulence and infection rate of several pathogenic bacteria, such as Neisseria meningitidis and Pseudomonas aeruginosa, are strongly dependent on the presence of pili as they facilitate the adhesion of the bacteria to the host cell. Disruption of the interactions between the pili and the host cells by targeting proteins involved in this interaction could, therefore, be a treatment strategy. A type IV pilus is primarily composed of multiple copies of protein subunits called major pilins. Additional proteins, called minor pilins, are present in lower abundance, but are essential for the assembly of the pilus or for its specific functions. One class of minor pilins is required to initiate the formation of pili, and may form a complex similar to that identified in the related type II secretion system. Other, species-specific minor pilins in the type IV pilus system have been shown to promote additional functions such as DNA binding, aggregation and adherence. Here, we will review the structure and the function of the minor pilins from type IV pili. Keywords Type IV pili • Minor pilins • Adhesion • Type II secretion system Abbreviations T2SS Type II secretion system T4P Type IV pilus T4aP Type IVa pilus T4bP Type IVb pilus

Transposon Insertion Sequencing in a Clinical Isolate of Legionella pneumophila Identifies Essential Genes and Determinants of Natural Transformation

“…With the remarkable exception of Helicobacter pylori (65), in all Gram-negative bacteria DNA uptake requires type IV pili (20). Type IV pili are extracellular filaments resulting from the assembly of thousands copies of an abundant major pilin but also of less abundant minor pilins that could be embedded in the filaments (core minor pilins) or at its tip (non-core minor pilins) (66,67). The nomenclature of pilins is relatively confusing but the major pilin is generally called PilA, although in Neisseria sp.…”

“…This indicates that PilE, while not strictly essential still plays a role in pilus formation. Minor pilins have been proposed to localize at the tip of the pilus and stabilize it (66). In Vibrio cholerae, DNA binding has been observed to occur at the tip of the pilus (21).…”

“…In the latter system, the last three genes (gspIJK) encode minor pseudopilins which assemble into a stable complex (71). This complex of minor pilins would form in the inner membrane to establish a platform for the assembly of the major pilin (72), and remain at the tip of the pilus, stabilizing it (66). Such heterotrimeric complex may be formed by minor pilins of limited homology but displaying structural similarity (73).…”

Biogenesis of Type V pili

“…54 Pilus formation is initiated by the minor pilin complex that stabilizes the tip of pilus and provides a template for the assembly of major subunits. 55 Pilus elongation and retraction are mediated by PilC, and two antagonistic ATPases, PilB, and PilT. 56,57 The structures and molecular weights of the minor pilins are different from those of the major pilin.…”

Transposon-insertion sequencing in a clinical isolate ofLegionella pneumophilaidentifies essential genes and determinants of natural transformation

“…With the remarkable exception of Helicobacter pylori (62), in all Gram-negative bacteria DNA uptake requires type IV pili (19). Type IV pili are extracellular filaments resulting from the assembly of thousands copies of an abundant major pilin but also of less abundant minor pilins that could be embedded in the filaments (core minor pilins) or at its tip (non-core minor pilins) (63,64). The nomenclature of pilins is relatively confusing but the major pilin is generally called PilA, although in Neisseria sp.…”