Related Experiment Videos
Localization of biologically important regions on toxic shock syndrome toxin 1
D L Murray1, C A Earhart, D T Mitchell
1Department of Microbiology, University of Minnesota Medical School, Minneapolis 55455, USA.
Abstract:
Toxic shock syndrome toxin 1 (TSST-1) contains a long central alpha helix that forms the base of two grooves on opposite sides of the molecule. Previous studies indicated that residues 132, 135, and 140 along the back of the central alpha helix are important in the biological activities. We made mutations of additional central alpha-helix residues exposed along this groove on the back of TSST-1. The proteins were purified, shown not to have gross alteration in structure, and tested for both superantigenicity and ability to elicit lethal TSS, using the superantigenicity, likely to because of alteration in T-cell receptor binding. Mutants H135A, Q136A, and E132K/ Q136K lost the ability to induce lethal TSS. The mutant Q136A was most increasing because it was superantigenic, yet nonlethal.
Insights
Mutations in toxic shock syndrome toxin 1 (TSST-1) central alpha helix residues were studied. Some mutations abolished lethal toxic shock syndrome (TSS) induction while retaining superantigenicity, indicating specific structural roles.
Area of Science:
- Microbiology
- Immunology
- Structural Biology
Background:
- Toxic shock syndrome toxin 1 (TSST-1) is a superantigen produced by Staphylococcus aureus.
- TSST-1 possesses a central alpha helix with grooves implicated in biological activity.
- Previous research identified key residues (132, 135, 140) in this helix.
Purpose of the Study:
- To investigate the role of additional central alpha-helix residues in TSST-1 function.
- To determine how mutations affect TSST-1 superantigenicity and lethal toxic shock syndrome (TSS) induction.
- To understand the structural basis of T-cell receptor binding.
Main Methods:
- Site-directed mutagenesis of TSST-1 central alpha-helix residues.
- Protein purification and structural integrity assessment.
- In vitro testing of superantigenic activity and in vivo lethality assays for TSS induction.
Main Results:
- Mutants H135A, Q136A, and E132K/Q136K lost the ability to induce lethal TSS.
- The Q136A mutant remained superantigenic but did not cause lethal TSS.
- Structural integrity of the mutated proteins was confirmed.
Conclusions:
- Specific residues within the TSST-1 central alpha helix are critical for inducing lethal TSS.
- Dissociation of superantigenicity from lethality is possible through targeted mutagenesis.
- Alterations in T-cell receptor binding likely underlie the observed functional changes.