title: YscU cleavage and the assembly of Yersinia type III secretion machine complexes.
abstract: YscU, a component of the Yersinia type III secretion machine, promotes auto-cleavage at asparagine 263 (N263). Mutants with an alanine substitution at yscU codon 263 displayed secretion defects for some substrates (LcrV, YopB and YopD); however, transport of effector proteins into host cells (YopE, YopH, YopM) continued to occur. Two yscU mutations were isolated that, unlike N263A, completely abolished type III secretion; YscU(G127D) promoted auto-cleavage at N263, whereas YscU(G270N) did not. When fused to glutathione S-transferase (Gst), the YscU C-terminal cytoplasmic domain promoted auto-cleavage and Gst-YscU(C) also exerted a dominant-negative phenotype by blocking type III secretion. Gst-YscU(C/N263A) caused a similar blockade and Gst-YscU(C/G270N) reduced secretion. Gst-YscU(C) and Gst-YscU(C/N263A) bound YscL, the regulator of the ATPase YscN, whereas Gst-YscU(C/G270N) did not. When isolated from Yersinia, Gst-YscU(C) and Gst-YscU(C/N263A) associated with YscK-YscL-YscQ; however, Gst-YscU(C/G270N) interacted predominantly with the machine component YscO, but not with YscK-YscL-YscQ. A model is proposed whereby YscU auto-cleavage promotes interaction with YscL and recruitment of ATPase complexes that initiate type III secretion.
authors.affiliation: Department of Microbiology, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Riordan
authors.forename: Olaf
authors.initials: O
authors.lastname: Schneewind
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006367:HeLa Cells; D006801:Humans; D009154:Mutation; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D015007:Yersinia / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D020033:Protein Isoforms