Structural and functional analogy between pneumolysin and proaerolysin

Pneumolysin and proaerolysin are bacterial toxins that form pores in hostcells by oligomerization. We propose that they may have similar structuresdespite a poor sequence identity. The crystal structure of proaerolysinreveals a protein composed of four domains, arranged in the shape of anelongated comma. Electron microscopy of the pneumolysin monomer shows asimilar arrangement of domains. The sequence of pneumolysin recognizes thetemplate of proaerolysin from a library of protein folds. Athree-dimensional model of pneumolysin has been constructed by thecomparative approach using the structure of proaerolysin. This model,together with results on the activity of site- specific mutants and thepositions of antigenic sites, has been used to propose functional roles ofindividual domains.