title: Dual amyloid domains promote differential functioning of the chaplin proteins during Streptomyces aerial morphogenesis.
abstract: The chaplin proteins are functional amyloids found in the filamentous Streptomyces bacteria. These secreted proteins are required for the aerial development of Streptomyces coelicolor, and contribute to an intricate rodlet ultrastructure that decorates the surfaces of aerial hyphae and spores. S. coelicolor encodes eight chaplin proteins. Previous studies have revealed that only three of these proteins (ChpC, ChpE, and ChpH) are necessary for promoting aerial development, and of these three, ChpH is the primary developmental determinant. Here, we show that the model chaplin, ChpH, contains two amyloidogenic domains: one in the N terminus and one in the C terminus of the mature protein. These domains have different polymerization properties as determined using fluorescence spectroscopy, secondary structure analyses, and electron microscopy. We coupled these in vitro assays with in vivo genetic studies to probe the connection between ChpH amyloidogenesis and its biological function. Using mutational analyses, we demonstrated that both N- and C-terminal amyloid domains of ChpH were required for promoting aerial hypha formation, while the N-terminal domain was dispensable for assembly of the rodlet ultrastructure. These results suggest that there is a functional differentiation of the dual amyloid domains in the chaplin proteins.
authors.affiliation: Department of Biology and MG DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main Street West, Hamilton, ON, Canada L8S 4K1.
authors.forename: David S
authors.initials: DS
authors.lastname: Capstick
authors.forename: Ahmad
authors.initials: A
authors.lastname: Jomaa
authors.forename: Chistopher
authors.initials: C
authors.lastname: Hanke
authors.forename: Joaquin
authors.initials: J
authors.lastname: Ortega
authors.forename: Marie A
authors.initials: MA
authors.lastname: Elliot
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D058227:Amyloidogenic Proteins / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D017353:Gene Deletion; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation; D017386:Sequence Homology, Amino Acid; D048372:Streptomyces coelicolor / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure
chemical_list: D000682:Amyloid; D058227:Amyloidogenic Proteins; D001426:Bacterial Proteins