Subunit composition of a bicomponent toxin: Staphylococcal leukocidin forms an octameric transmembrane pore

Abstract

Staphylococcal leukocidin pores are formed by the obligatory interaction of two distinct polypeptides, one of class F and one of class S, making them unique in the family of ␤-barrel pore-forming toxins (␤-PFTs). By contrast, other ␤-PFTs form homo-oligomeric pores; for example, the staphylococcal ␣-hemolysin (␣HL) pore is a homoheptamer. Here, we deduce the subunit composition of a leukocidin pore by two independent methods: gel shift electrophoresis and site-specific chemical modification during single-channel recording. Four LukF and four LukS subunits coassemble to form an octamer. This result in part explains properties of the leukocidin pore, such as its high conductance compared to the ␣HL pore. It is also pertinent to the mechanism of assembly of ␤-PFT pores and suggests new possibilities for engineering these proteins.

Crystal structure of the octameric pore of staphylococcal γ-hemolysin reveals the β-barrel pore formation mechanism by two components

“…This agreed well with several previous reports showing that the pore of bicomponent β-PFTs prepared on cells consisted of four molecules of each of the F and S components (22)(23)(24)(25). In contrast, several reports indicated that γHL pores formed on the erythrocyte membrane are mainly composed of six (17,26) or seven protomers (12,20,34).…”

“…Electron microscopy and cross-linking experiments of purified γHL pores on human erythrocyte membranes demonstrated the existence of a heptamer with a 3∶4 or 4∶3 molar ratio of F to S components (20,21), whereas biochemical analyses of pores of engineered covalent γHL heterodimers on erythrocytes and leukocytes suggested octameric stoichiometry (22). Several reports using LUK pores formed on rabbit erythrocytes also demonstrated the existence of an octamer consisting of 4-plus-4 subunits (23)(24)(25). However, hexamer was also proposed based on structure modeling using monomeric structures of PVL (17) and electron microscopy of LUK pores on leukocytes and erythrocytes (26).…”

TLR 2 and CD14 Mediate Innate Immunity and Lung Inflammation to Staphylococcal Panton–Valentine Leukocidin In Vivo

“…4A). These data are in line with previous observations, showing that both subunits of PVL in an equimolar ratio are required to perform a pore (10). Significantly, although single subunits were incapable of forming a pore in MH-S cells, LukS was capable of inducing TNF-a gene expression (Fig.…”

“…PVL consists of two subunits, LukS-PV and LukF-PV, which, in an equimolar ratio, shape the octamer structure that is essential for pore formation on host cells (9,10). Previous studies show that human and rabbit neutrophils are highly sensitive to the poreforming properties of PVL and rapidly undergo cell death (11,12).…”

Bacterial Two-component and Hetero-heptameric Pore-forming Cytolytic Toxins: Structures, Pore-forming Mechanism, and Organization of the Genes

“…10) Miles et al reported that LukF and LukS of Luk form an octameric transmembrane pore. 36) This conclusion was based on the results obtained from gel shift electrophoresis and site-specific chemical modification during single-channel recording. 36) Is the complex hexameric, heptameric, or octameric, then?…”