Bacterial flagella and type III secretion systems

Certain classes of pathogenic bacteria secrete virulence proteins in a Sec- independent manner, by a mechanism known as type III secretion. The main bo dy of the export apparatus specific for virulence proteins is identified as a needle complex, which has a similar structural organization to flagella. The two structures share several proteins with highly homologous amino aci d sequences. Even where the sequence identity is low among flagellar protei ns from various species, the physico-chemical properties of each protein re main homologous. Therefore, by comparing the physico-chemical properties of unidentified proteins, it is possible to find homologs among type III secr etion systems. (C) 2001 Federation of European Microbiological Societies. P ublished by Elsevier Science B.V. All rights reserved.