Crystal Structure of Cytotoxin Protein Suilysin From Streptococcus Suis

Protein Cell. 2010 Jan;1(1):96-105. doi: 10.1007/s13238-010-0012-3. Epub 2010 Feb 7.


Cholesterol-dependent cytolysins (CDC) are pore forming toxins. A prototype of the CDC family members is perfringolysin O (PFO), which directly binds to the cell membrane enriched in cholesterol, causing cell lysis. However, an exception of this general observation is intermedilysin (ILY) of Streptococcus intermedius, which requires human CD59 as a receptor in addition to cholesterol for its hemolytic activity. A possible explanation of this functional difference is the conformational variation between the C-terminal domains of the two toxins, particularly in the highly conserved undecapeptide termed tryptophan rich motif. Here, we present the crystal structure of suilysin, a CDC toxin from the infectious swine pathogen Streptococcus suis. Like PFO, suilysin does not require a host receptor for hemolytic activity; yet the crystal structure of suilysin exhibits a similar conformation in the tryptophan rich motif to ILY. This observation suggests that the current view of the structure-function relationship between CDC proteins and membrane association is far from complete.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Bacterial Toxins / chemistry
  • Bacteriocins / chemistry
  • Cholesterol / chemistry
  • Crystallography, X-Ray
  • Cytotoxins / chemistry*
  • Hemolysin Proteins / chemistry*
  • Hemolysin Proteins / genetics
  • Molecular Sequence Data
  • Point Mutation
  • Protein Structure, Tertiary
  • Sequence Alignment
  • Streptococcus suis / metabolism*
  • Swine


  • Bacterial Toxins
  • Bacteriocins
  • Cytotoxins
  • Hemolysin Proteins
  • intermedilysin protein, Streptococcus intermedius
  • suilysin
  • Clostridium perfringens theta-toxin
  • Cholesterol

Associated data

  • PDB/3HVN