NMR identification of the binding surfaces involved in the Salmonella and Shigella Type III secretion tip-translocon protein-protein interactions.
The type III secretion system (T3SS) is essential for the pathogenesis of many bacteria including Salmonella and Shigella, which together are responsible for millions of deaths worldwide each year. The structural component of the T3SS consists of the needle apparatus, which is assembled in part by the protein-protein interaction between the tip and the translocon. The atomic detail of the interaction between the tip and the translocon proteins is currently unknown. Here, we used NMR methods to identify that the N-terminal domain of the Salmonella SipB translocon protein interacts with the SipD tip protein at a surface at the distal region of the tip formed by the mixed α/β domain and a portion of its coiled-coil domain. Likewise, the Shigella IpaB translocon protein and the IpaD tip protein interact with each other using similar surfaces identified for the Salmonella homologs. Furthermore, removal of the extreme N-terminal residues of the translocon protein, previously thought to be important for the interaction, had little change on the binding surface. Finally, mutations at the binding surface of SipD reduced invasion of Salmonella into human intestinal epithelial cells. Together, these results reveal the binding surfaces involved in the tip-translocon protein-protein interaction and advance our understanding of the assembly of the T3SS needle apparatus. Proteins 2016; 84:1097-1107. © 2016 Wiley Periodicals, Inc.
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045.
Andrew C
AC
McShan
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045.
Kawaljit
K
Kaur
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, 63110.
Srirupa
S
Chatterjee
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599.
Kevin M
KM
Knight
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, 66045.
Roberto N
RN
De Guzman
D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology; D015870:Gene Expression; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012475:Salmonella / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D012760:Shigella / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D000069296:Type III Secretion Systems / Q000235:genetics / Q000378:metabolism
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C095770:IpaD protein, Shigella flexneri; D008565:Membrane Proteins; D011994:Recombinant Proteins; C107188:SspD protein, Salmonella typhimurium; D000069296:Type III Secretion Systems; C094579:invasion protein B, Salmonella typhimurium; C087447:ipaB protein, Shigella
IpaB; IpaD; NMR spectroscopy; SipB; SipD; Type III secretion system; tip; translocon