Virulence Mechanisms World of Bacterial Pathogens: Role in Tetratricopeptide Repeat Motifs in the

SUMMARY AND CONCLUDING REMARKS TPRs occur ubiquitously in organisms as diverse as bacteria andhumans.TheevolutionaryconservationoftheTPRmotifsuggeststhatitisfundamentallyimportantforlivingorganisms,function-ingasamoduleforprotein-proteininteractions.TPR-containingproteins are involved in a variety of cellular functions, includingthose that participate in bacterial pathogenesis (3, 37). Usingbioinformatics, a number of TPR-containing virulence factorshavebeenpredicted,stimulatinginvestigationfocusedonmolec-ular aspects of bacterial pathogenesis mediated by TPR motifs.OftheTPRvirulencefactorsproposed,classIIchaperonesofabacterial TTSS of Y . pestis (LcrH), P . aeruginosa (PcrH), and Shi-gella (IpgC)havebeenexperimentallyshowntodisplayTPRmo-tifs.TherolesofTPRmotifswithintheseproteinshavebeenspec-ified, demonstrating that TPR motifs crucially determine thefunctioningofLcrH,PcrH,andIpgCbygivingthemtheabilitytobind and stabilize the respective translocator proteins in the bac-terialcytoplasm(6,7,9,34).Furthermore,aTPRdomainenablesclass II chaperones to self-assemble homodimers (6, 7, 9, 68), anarrangementthatisparticularlyrequiredfortheproperbiologicalfunctioning of LcrH and IpgC (6, 9, 68). Besides class II chaper-onesofaTTSS,TPR-containingproteinshavealsobeensuggestedto participate in virulence apparatuses of bacteria such as