title: Delineation and characterization of the actin nucleation and effector translocation activities of Salmonella SipC.
abstract: Salmonella type III secreted SipC possesses dual functions: translocation of effectors and actin modulation. The biological significance of SipC's actin nucleation activity in Salmonella-induced actin cytoskeleton rearrangements has not been studied. We report here the delineation of the actin nucleation activity from the effector translocation activity of SipC. Our data show that the central amino acid region (residues: 201-220) is essential for its actin nucleation activity and the C-terminal amino acid region (321-409) is required for translocation of effectors. A SipC nucleation-deficient mutant, which maintained its effector translocation activity, was obtained. This nucleation-deficient mutant had significantly reduced ability to induce actin cytoskeleton rearrangements, resulting in lower bacterial invasion into HeLa cells. Contrary to a previous report, we found that the purified recombinant wild-type SipC(199-409) protein is monomeric in solution by size exclusion chromatography coupled with multiangle laser light scattering assays (SEC-LS). Our data established that the actin nucleation activity of SipC plays a vital role in Salmonella-induced membrane ruffles and subsequent bacteria invasion.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: JiHoon
authors.initials: J
authors.lastname: Chang
authors.forename: Jue
authors.initials: J
authors.lastname: Chen
authors.forename: Daoguo
authors.initials: D
authors.lastname: Zhou
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000737:chemistry; D006367:HeLa Cells; D006801:Humans; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012486:Salmonella typhimurium / Q000378:metabolism* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D011993:Recombinant Fusion Proteins; C094578:Salmonella invasion protein C