Assembly of Adhesive Organelles on Gram-Negative Bacteria

F4 Fimbriae Expressed by Porcine Enterotoxigenic <i>Escherichia coli</i>, an Example of an Eccentric Fimbrial System?

“…Therefore, like for several fimbrial systems, the subunit-subunit interactions between F4 fimbriae are also supposed to rely on the mechanism of donor strand exchange [Barnhart et al, 2000;Knight et al, 2000]. This mechanism is best characterized in P pili and type I fimbriae of E. coli and in F1 fimbriae of Yersinia pestis [Soto et al, 1998;Barnhart et al, 2003;Zavialov et al, 2003aZavialov et al, , 2003b (fig. 4).…”

“…In type 1 and P pili, the relative affinity of each chaperone-subunit complex for the usher correlates with the final position of the respective subunit in the pilus Jacob-Dubuisson et al, 1993;Saulino et al, 1998]. In addition, it is discovered that the information necessary for targeting the chaperone-subunit complex to the usher resides mainly in the subunit protein [Barnhart et al, 2003;Nishiyama et al, 2003]. …”

“…The incoming N-terminus during donor strand exchange runs antiparallel to the subunit 'F' ß-strand, in contrast to the 'G' ß-strand of the chaperone. So, the subunit undergoes a topological transition from a non-canonical to a canonical Ig fold, resulting in more closed conformation of the groove and driving subunit assembly into a fibre [Sauer et al, 2002;Barnhart et al, 2003;Zavialov et al, 2003a]. These energetically favourable conformational changes during pilus assembly are very important since the mode of action of fimbrial chaperones is independent of cellular energy [Jacob-Dubuisson et al, 1994b].…”

“…The Cand N-termini of the subunits are indicated, as well as the names of the ß-strands. The names of the strands are according to the Ppilus subunits [according to Justice et al, 2003]. …”