An important event in signal transduction is the binding of SH3 domain
s, found in viral proteins such as v-Src and v-Crk, to proline-rich se
quences. Recently, proline-rich proteins that bind host-cell SH3 domai
ns have been identified in a variety of pathogenic microorganisms. Exp
loitation of SH3-mediated interactions by pathogens may be more common
than previously suspected.