The SpeB virulence factor of Streptococcus pyogenes, a multifunctional secreted and cell surface molecule with strepadhesin, laminin-binding and cysteine protease activity

The interactions between pathogenic bacteria and the host need to be resolv ed at the molecular level in order to develop novel vaccines and drugs. We have previously identified strepadhesin, a novel glycoprotein-binding activ ity in Streptococcus pyogenes, which is regulated by Mga, a regulator of st reptococcal virulence factors. We have now identified the protein responsib le for the strepadhesin activity and find that (i) strepadhesin activity is carried by SpeB, streptococcal pyrogenic exotoxin with cysteine protease a ctivity; (ii) SpeB carries laminin-binding activity of the bacteria; and (i ii) SpeB is not only a secreted molecule but also occurs unexpectedly tight ly bound to the bacterial cell surface. Thus, in contrast to the previous v iew of SpeB as mainly an extracellular protease, it is also present as a st reptococcal surface molecule with binding activity to laminin and other gly coproteins.