title: BfpL is essential for type IV bundle-forming pilus biogenesis and interacts with the periplasmic face of BfpC.
abstract: Enteropathogenic Escherichia coli (EPEC) causes diarrhoea among infants in developing countries. The bundle-forming pilus (BFP), a type IV pilus found on the surface of EPEC, is essential for full virulence of typical EPEC strains. The machinery for BFP assembly and function is encoded by an operon of 14 genes. Here we investigate the role in pilus biogenesis of BfpL, a small protein with a single N-terminal predicted transmembrane domain reminiscent of pilin-like proteins. We confirmed that a bfpL mutant lacks BFP, and associated auto-aggregation and localized adherence phenotypes. Furthermore, we found that a double mutant unable to express both the putative retraction ATPase BfpF and BfpL also lacks BFP and associated phenotypes, distinguishing BfpL from pilin-like proteins. Western blots of sheared pilus preparations did not suggest that BfpL is a component of BFP. Topology studies using C-terminal truncations and a dual reporter revealed that most of the BfpL protein resides in the periplasm. Further, we demonstrated through yeast two-hybrid assays and confirmed by fluorescence anisotropy that BfpL interacts with the periplasmic face of BfpC. Thus, BfpL has a function distinct from those of pilin-like proteins and is instead part of an inner-membrane subassembly complex that is believed to extract bundlin, the main pilus subunit, from the inner membrane to be incorporated into BFP.
authors: Division of Infectious Diseases, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors: Leon
authors: L
authors: De Masi
authors: Center for Fluorescence Spectroscopy, Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors: Henryk
authors: H
authors: Szmacinski
authors: Division of Infectious Diseases, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors: Wiebke
authors: W
authors: Schreiber
authors: Division of Infectious Diseases, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
authors: Michael S
authors: MS
authors: Donnenberg
mesh_terms: D000595:Amino Acid Sequence; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D036781:Fimbriae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D020043:Genes, Essential; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019897:Periplasm / Q000378:metabolism*; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques
chemical_list: C502813:BfpC protein, E coli; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D036781:Fimbriae Proteins