title: Assembly of streptolysin O pores assessed by quartz crystal microbalance and atomic force microscopy provides evidence for the formation of anchored but incomplete oligomers.
abstract: Streptolysin O (SLO) is a bacterial pore forming protein that is part of the cholesterol dependent cytolysin (CDC) family. We have used quartz crystal microbalance with dissipation monitoring (QCM-D) to examine SLO membrane binding and pore formation. In this system, SLO binds tightly to cholesterol-containing membranes, and assembles into partial and complete pores confirmed by atomic force microscopy. SLO binds to the lipid bilayer at a single rate consistent with the Langmuir isotherm model of adsorption. Changes in dissipation illustrate that SLO alters the viscoelastic properties of the bilayer during pore formation, but there is no loss of material from the bilayer as reported for small membrane-penetrating peptides. SLO mutants were used to further dissect the assembly and insertion processes by QCM-D. This shows the signature of SLO in QCM-D changes when pore formation is inhibited, and that bound and inserted SLO forms can be distinguished. Furthermore a pre-pore locked SLO mutant binds reversibly to lipid, suggesting that the partially complete wtSLO forms observed by AFM are anchored to the membrane.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Stewart
authors.forename: Michael E
authors.initials: ME
authors.lastname: D'Angelo
authors.forename: Stefania
authors.initials: S
authors.lastname: Paintavigna
authors.forename: Rico F
authors.initials: RF
authors.lastname: Tabor
authors.forename: Lisandra L
authors.initials: LL
authors.lastname: Martin
authors.forename: Phillip I
authors.initials: PI
authors.lastname: Bird
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D018625:Microscopy, Atomic Force / Q000379:methods*; D008954:Models, Biological; D009154:Mutation; D011485:Protein Binding; D055503:Protein Multimerization; D058525:Quartz Crystal Microbalance Techniques / Q000379:methods*; D012756:Sheep; D013301:Streptolysins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D013301:Streptolysins; C025964:streptolysin O; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine