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The 28k and 70k dalton polypeptide components of mouse Ra-reactive factor are responsible for bactericidal activity
I Ihara1, S Ihara, A Nagashima
1Department of Molecular Biology, School of Medicine, Kitasato University, Kanagawa-ken, Japan.
Abstract:
Ra-reactive factor is a complement-dependent bactericidal factor that reacts specifically with Ra chemotype strains of Salmonella, and is ubiquitous in sera of a wide variety of vertebrates. Here we prepared an antiserum by immunizing rabbit with mouse Ra-reactive factor. This serum neutralized markedly the bactericidal activity of the factor. This action of the antiserum was inhibited by the factor whose bactericidal activity has been inactivated by heating for 30 min at 55 degrees C. Component polypeptides with apparent molecular weights of 28k and 70k in the factor were separated by SDS-polyacrylamide gel electrophoresis. They were also found to inhibit the antiserum activity. This indicates that these polypeptides carry the active site of the factor.
Insights
Researchers identified key components of Ra-reactive factor, a bactericidal agent. This factor, crucial for innate immunity, targets specific Salmonella strains. The study pinpoints active polypeptides responsible for its antimicrobial function.
Area of Science:
- Immunology
- Microbiology
- Biochemistry
Background:
- Ra-reactive factor is a complement-dependent bactericidal substance found in vertebrate sera.
- It specifically targets Ra chemotype strains of Salmonella, playing a role in innate immunity.
- Understanding its components is crucial for elucidating its mechanism of action.
Purpose of the Study:
- To characterize the active components of the mouse Ra-reactive factor.
- To identify the specific polypeptides responsible for the factor's bactericidal activity.
- To investigate the role of these polypeptides in the factor's interaction with its target.
Main Methods:
- Preparation of rabbit antiserum against mouse Ra-reactive factor.
- Assay of bactericidal activity neutralization by the antiserum.
- Heat inactivation of Ra-reactive factor to assess antiserum inhibition.
- Separation of factor polypeptides using SDS-polyacrylamide gel electrophoresis.
Main Results:
- The prepared antiserum significantly neutralized the bactericidal activity of Ra-reactive factor.
- Heat-inactivated factor inhibited the antiserum's action, confirming specificity.
- SDS-PAGE revealed two component polypeptides (28 kDa and 70 kDa) within the factor.
- These isolated polypeptides also inhibited the antiserum's activity, indicating they contain the active site.
Conclusions:
- The study identified 28 kDa and 70 kDa polypeptides as carrying the active site of Ra-reactive factor.
- These findings provide insights into the molecular basis of Ra-reactive factor's bactericidal function.
- This characterization advances the understanding of Salmonella-specific innate immune mechanisms.