title: Specific protein-membrane contacts are required for prepore and pore assembly by a cholesterol-dependent cytolysin.
abstract: Three short hydrophobic loops and a conserved undecapeptide at the tip of domain 4 (D4) of the cholesterol-dependent cytolysins (CDCs) mediate the binding of the CDC monomers to cholesterol-rich cell membranes. But intermedilysin (ILY), from Streptococcus intermedius, does not bind to cholesterol-rich membranes unless they contain the human protein CD59. This observation suggested that the D4 loops, which include loops L1-L3 and the undecapeptide, of ILY were no longer required for its cell binding. However, we show here that membrane insertion of the D4 loops is required for the cytolysis by ILY. Receptor binding triggers changes in the structure of ILY that are necessary for oligomerization, but membrane insertion of the D4 loops is critical for oligomer assembly and pore formation. Defects that prevent membrane insertion of the undecapeptide also block assembly of the prepore oligomer, while defects in the membrane insertion of the L1-L3 loops prevent the conversion of the prepore oligomer to the pore complex. These studies reveal that pore formation by ILY, and probably other CDCs, is affected by an intricate and coupled sequence of interactions between domain 4 and the membrane.
authors.affiliation: Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Casie E
authors.initials: CE
authors.lastname: Soltani
authors.forename: Eileen M
authors.initials: EM
authors.lastname: Hotze
authors.forename: Arthur E
authors.initials: AE
authors.lastname: Johnson
authors.forename: Rodney K
authors.initials: RK
authors.lastname: Tweten
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001430:Bacteriocins / Q000737:chemistry* / Q000378:metabolism; D018957:CD59 Antigens / Q000737:chemistry* / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry* / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D011485:Protein Binding / Q000502:physiology; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D034367:Streptococcus intermedius / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D001430:Bacteriocins; D018957:CD59 Antigens; C403910:intermedilysin protein, Streptococcus intermedius; C051590:CD59 protein, human; D002784:Cholesterol