FILAMENTOUS PHAGE ASSEMBLY - VARIATION ON A PROTEIN EXPORT THEME

Biogenesis of both filamentous phage and type-IV pill involves the ass embly of many copies of a small, integral inner membrane protein (the phage major coat protein or pilin) into a helical, tubular array that passes through the outer membrane. The occurrence of related proteins required for assembly and export in both systems suggests that there m ay be similarities at the mechanistic level as well. This report summa rizes the properties of filamentous phage and the proteins required fo r their assembly, with particular emphasis on features they may share with bacterial protein export and pilus biogenesis systems, and it pre sents evidence that supports the hypothesis that one of the phage prot eins functions as an outer membrane export channel.