title: Type 3 Secretion Translocators Spontaneously Assemble a Hexadecameric Transmembrane Complex.
abstract: A type 3 secretion system is used by many bacterial pathogens to inject proteins into eukaryotic cells. Pathogens insert a translocon complex into the target eukaryotic membrane by secreting two proteins known as translocators. How these translocators form a translocon in the lipid bilayer and why both proteins are required remains elusive. Pseudomonas aeruginosa translocators PopB and PopD insert pores into membranes forming homo- or hetero-complexes of undetermined stoichiometry. Single-molecule fluorescence photobleaching experiments revealed that PopD formed mostly hexameric structures in membranes, whereas PopB displayed a bi-modal distribution with 6 and 12 subunits peaks. However, individually the proteins are not functional for effector translocation. We have found that when added together, the translocators formed distinct hetero-complexes containing 8 PopB and 8 PopD molecules. Thus, the interaction between PopB and PopD guide the assembly of a unique hetero-oligomer in membranes.
authors.affiliation: From the Program in Molecular and Cellular Biology, and.
authors.forename: Fabian B
authors.initials: FB
authors.lastname: Romano
authors.affiliation: From the Program in Molecular and Cellular Biology, and.
authors.forename: Yuzhou
authors.initials: Y
authors.lastname: Tang
authors.affiliation: the Departments of Biochemistry and Molecular Biology and.
authors.forename: Kyle C
authors.initials: KC
authors.lastname: Rossi
authors.affiliation: From the Program in Molecular and Cellular Biology, and.
authors.forename: Kathryn R
authors.initials: KR
authors.lastname: Monopoli
authors.affiliation: From the Program in Molecular and Cellular Biology, and Physics, University of Massachusetts, Amherst, Massachusetts 01003.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Ross
authors.affiliation: From the Program in Molecular and Cellular Biology, and the Departments of Biochemistry and Molecular Biology and heuck@umass.edu.
authors.forename: Alejandro P
authors.initials: AP
authors.lastname: Heuck
mesh_terms: D000942:Antigens, Bacterial / Q000737:chemistry* / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D011485:Protein Binding; D055503:Protein Multimerization; D011550:Pseudomonas aeruginosa; D000069296:Type III Secretion Systems / Q000737:chemistry* / Q000502:physiology
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D008051:Lipid Bilayers; C576076:PopB protein, Pseudomonas aeruginosa; D000069296:Type III Secretion Systems
keywords: membrane protein; membrane transport; oligomer; protein translocation; single-molecule biophysics; type III secretion system (T3SS)