Characterization of a streptococcal cholesterol-dependent cytolysin with a lewis y and b specific lectin domain.
The cholesterol-dependent cytolysins (CDCs) are a large family of pore-forming toxins that often exhibit distinct structural changes that modify their pore-forming activity. A soluble platelet aggregation factor from Streptococcus mitis (Sm-hPAF) was characterized and shown to be a functional CDC with an amino-terminal fucose-binding lectin domain. Sm-hPAF, or lectinolysin (LLY) as renamed herein, is most closely related to CDCs from Streptococcus intermedius (ILY) and Streptococcus pneumoniae (pneumolysin or PLY). The LLY gene was identified in strains of S. mitis, S. pneumoniae, and Streptococcus pseudopneumoniae. LLY induces pore-dependent changes in the light scattering properties of the platelets that mimic those induced by platelet aggregation but does not induce platelet aggregation. LLY monomers form the typical large homooligomeric membrane pore complex observed for the CDCs. The pore-forming activity of LLY on platelets is modulated by the amino-terminal lectin domain, a structure that is not present in other CDCs. Glycan microarray analysis showed the lectin domain is specific for difucosylated glycans within Lewis b (Le (b)) and Lewis y (Le (y)) antigens. The glycan-binding site is occluded in the soluble monomer of LLY but is apparently exposed after cell binding, since it significantly increases LLY pore-forming activity in a glycan-dependent manner. Hence, LLY represents a new class of CDC whose pore-forming mechanism is modulated by a glycan-binding domain.
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Stephen
S
Farrand
Eileen
E
Hotze
Paul
P
Friese
Susan K
SK
Hollingshead
David F
DF
Smith
Richard D
RD
Cummings
George L
GL
Dale
Rodney K
RK
Tweten
D000595:Amino Acid Sequence; D002784:Cholesterol / Q000378:metabolism*; D003603:Cytotoxins / Q000737:chemistry* / Q000235:genetics; D005452:Fluoresceins / Q000378:metabolism; D005798:Genes, Bacterial; D006461:Hemolysis; D006801:Humans; D037102:Lectins / Q000737:chemistry*; D007983:Lewis Blood Group Antigens / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry*; D010974:Platelet Aggregation; D011134:Polysaccharides / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013291:Streptococcus / Q000737:chemistry* / Q000235:genetics
C500822:3-aminopropyl fucopyranosyl-1-2-galactopyranosyl-1-3-(fucopyranosyl-1-4)-2-acetamido-2-deoxyglucopyranosyl-1-3-galactopyranosyl-1-4-glucopyranoside; D003603:Cytotoxins; D005452:Fluoresceins; D037102:Lectins; D007983:Lewis Blood Group Antigens; C094162:Lewis Y antigen; D009844:Oligosaccharides; D011134:Polysaccharides; D002784:Cholesterol; C007740:fluorexon