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Surface-associated host proteins on virulent Treponema pallidum
Abstract:
A surface coat of host serum proteins was detected on virulent Treponema pallidum by sodium dodecyl sulfate-gel electrophoresis. The loosely associated serum proteins could be removed by repeated washings in a protein-free medium. Washed T. pallidum retained the ability to readsorb numerous host proteins from rabbit serum as well as iodinated rabbit or human albumin. In addition, various avidly associated host serum proteins including albumin, alpha(2)-macroglobulin, transferrin, ceruloplasmin, immunoglobulin G, immunoglobulin M, and C3 were identified on the outer envelope of washed treponemes by an immunoadsorbent technique with protein A-bearing staphylococcus. Hyaluronidase treatment did not remove the avidly associated host proteins from the surface of washed treponemes, whereas trypsin treatment resulted in decreased levels of agglutination. Electrophoretic patterns of trypsin-treated treponemes showed that treponemal proteins as well as adsorbed host proteins were released concurrently by protease digestion. Reacquisition studies involving alpha(2)-macroglobulin and transferrin suggested the presence of noncompetitive binding sites for serum proteins on the treponemal outer envelope. Finally, differences among the T. pallidum preparations from individual rabbits with respect to incorporation of [(35)S]methionine, extent of agglutination with antisera, and length of time required for removal of avidly associated host proteins by trypsin treatment indicated biological variability among the treponemal populations.
Insights
Virulent Treponema pallidum acquires a surface coat of host serum proteins, which can be readsorbed after washing. These proteins are crucial for T. pallidum survival and exhibit biological variability.
Area of Science:
- Microbiology
- Immunology
- Protein Chemistry
Background:
- Virulent Treponema pallidum (T. pallidum) is the causative agent of syphilis.
- Understanding the interaction between T. pallidum and host proteins is crucial for developing effective treatments and diagnostics.
Purpose of the Study:
- To identify and characterize host serum proteins associated with the surface of virulent T. pallidum.
- To investigate the nature of the binding of these proteins and the biological variability of T. pallidum.
Main Methods:
- Sodium dodecyl sulfate-gel electrophoresis to detect surface proteins.
- Washing and readsorption assays to study protein binding.
- Immunoadsorbent techniques with protein A-bearing staphylococcus to identify specific proteins.
- Enzymatic treatments (hyaluronidase, trypsin) to assess protein removal.
- Radiolabeling with [(35)S]methionine to study protein incorporation.
Main Results:
- A surface coat of host serum proteins was detected on virulent T. pallidum.
- Loosely associated proteins were removed by washing, while avidly associated proteins (albumin, IgG, IgM, C3, etc.) remained.
- Washed treponemes could readsorb host proteins, indicating specific binding sites.
- Trypsin treatment removed both host and treponemal proteins, suggesting co-release.
- Biological variability was observed among T. pallidum preparations.
Conclusions:
- Virulent T. pallidum actively acquires and retains host serum proteins on its surface.
- The outer envelope of T. pallidum possesses binding sites for serum proteins.
- Biological variability in T. pallidum influences host protein interactions.