SnapShot:BacterialAppendagesIIAnaTosteRego,RémiFronzes,andGabrielWaksmanInstituteofStructuralMolecularBiology,BirkbeckandUniversityCollegeLondon,LondonWC1E7HX,UKSeeonlineversionforlegendandreferences.PartIappearedintheJanuary8issueofCell.294Cell140,January22,2010©2010ElsevierInc.DOI10.1016/j.cell.2010.01.006294.e1Cell140,January22,2010©2010ElsevierInc.DOI10.1016/j.cell.2010.01.006SnapShot:BacterialAppendagesIIAnaTosteRego,RémiFronzes,andGabrielWaksmanInstituteofStructuralMolecularBiology,BirkbeckandUniversityCollegeLondon,LondonWC1E7HX,UKThistwo-partSnapShotdepictstheassemblyandstructureofselectednonflagellarsurfaceappendagesfromgram-negativebacteria.Theseincludechaperone-usherpiliandtypeIVpili(inpartI)andthetypeIIIsecretionneedleandtypeIVsecretionpili(inpartII).TypeIIISecretionNeedle(Left)TypeIIIpili,alsocalledtheneedlecomplexorinjectisome,isananomachine(evolutionarilyrelatedtoflagellum)involvingover20proteins.Itiscomposedofabasalbodythatspansacrossbothouterandinnermembranes(OMandIM)andtheperiplasm(P)andanexternalneedleonthesurfaceofbacteria.Thebasalbody,shownherebythecryo-electronmicroscopy(cryo-EM)3DstructureoftheneedlecomplexofSalmonellatyphimurium(gray),consistsoftwodoublerings(InvGinredandPrgK/Hindarkblueandlightorange[Yipetal.,2005;Spreteretal.,2009])thatspantheIMandOMlinkedbyahollowstructure(PrgJinlightblue)thatcrossestheperiplasmicspace(Marlovitsetal.,2006).Onthecytoplasmicsideotheraccessoryproteins(SpaSinorangeandInvK/SpaOinyellow;Deaneetal.,2008)aswellasATPases(InvC/SpaLinlightgreen;Zarivachetal.,2007)areincontactwiththebasalbody(InvI/SpaP/SpaQ/InvN/SpaRandInvAarealsoaccessoryproteinsbutarenotrepresented).Theexternalneedleisahollowstructurecomposedofahomopolymerof100–150subunitsofPrgI(green;Deaneetal.,2006).InthedistalendoftheneedleatipcomplexcomposedofSipD(pink;Derewendaetal.,2004)isoneofthethreetranslocators(SipB,SipC,SipD)involvedinporeformation.TypeIVSecretionPili(Right)TypeIVsecretionsystemsareversatilesystemsthatarefoundinGram-negativeandGra...
