Streptococcal M protein: alpha-helical coiled-coil structure and arrangement on the cell surface.
Year: 1981
Type: article
Abstract: The conformation and molecular dimensions of purified type 6 streptococcal M proteins establish the close structural relationship of these molecules to tropomyosin. Ultracentrifuge studies reveal that the M molecules exist as stable dimers; circular dichroism spectra indicate that the molecules contain about 70% alpha helix; and fiber x-ray diffraction diagrams show the characteristic reflections of the alpha-helical pattern. Electron microscopic images of M protein shadowed with platinum reveal rod-shaped molecules having the same width as tropomyosin. However, the lengths of the M molecules are about 30% shorter than lengths predicted by assuming a completely alpha-helical molecule. These findings indicate that the structure of the M6 protein is primarily alpha-helical coiled coil. Comparison of the lengths of the fibers on the surface of the streptococcus and the isolated M proteins suggests that each fiber on the cell wall consists of a single M-protein molecule approximately 500 A long. The structure determined for these fimbriae is the first alpha-helical coiled-coil conformation to be demonstrated for bacterial surface projections.
Authors: G N Phillips, P F Flicker, C Cohen, B N Manjula, V A Fischetti
Institutions: Brandeis University, Rockefeller University
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2043875489