Dual amyloid domains promote differential functioning of the chaplin proteins during Streptomyces aerial morphogenesis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 24; pp. 9821 - 9826
• Main Authors: Capstick, David S, Jomaa, Ahmad, Hanke, Chistopher, Ortega, Joaquin, Elliot, Marie A
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 14.06.2011; National Acad Sciences
• Subjects: Amino Acid Sequence; Amyloid; Amyloid - genetics; Amyloid - physiology; Amyloid - ultrastructure; Amyloidogenesis; Amyloidogenic Proteins - genetics; Amyloidogenic Proteins - physiology; Amyloids; Bacteria; Bacterial Proteins - genetics; Bacterial Proteins - physiology; Bacterial Proteins - ultrastructure; Biological Sciences; Developmental biology; Differentiation; Electron microscopy; Fluorescence; fluorescence emission spectroscopy; fluorescence spectroscopy; Gene Deletion; Hyphae; in vitro studies; Microscopy, Electron; Molecular Sequence Data; Morphogenesis; Mutation; Plasmids; Polymerization; Probes; protein secretion; Protein structure; Proteins; Secondary structure; Sequence Homology, Amino Acid; Spectrum analysis; Spores; Streptomyces; Streptomyces coelicolor; Streptomyces coelicolor - genetics; Streptomyces coelicolor - growth & development; Streptomyces coelicolor - ultrastructure; Ultrastructure
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1018715108

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.