Mega assemblages of oligomeric aerolysin-like toxins stabilized by toxin-associating membrane proteins
Hiroyasu Shimada1, Sakae Kitada
1Department of Bioscience and Bioinfomatics, Kyushu Institute of Technology, Iizuka, Fukuoka 820-8502, Japan.
Abstract:
Most β pore-forming toxins need to be oligomerized via receptors in order to form membrane pores. Though oligomerizing toxins frequently form SDS-resistant oligomers, it was questionable whether SDS-resistant oligomers reflected native functional toxin complexes. In order to elucidate the essence of the cytocidal assemblages, oligomers of aerolysin-like toxins, aerolysin, parasporin-2 and epsilon toxin, were examined with or without SDS. On Blue Native PAGE, each toxin, which had been solubilized from target cells with mild detergent, was a much larger complex (nearly 1 MDa) than the typical SDS-resistant oligomers (∼200 kDa). Size exclusion chromatography confirmed the huge toxin complexes. While a portion of the huge complexes were sensitive to proteases, SDS-resistant oligomers resist the proteolysis. Presumably the core toxin complexes remained intact while the cellular proteins were degraded. Moreover, intermediate complexes, which included no SDS-resistant oligomers, could be detected at lower temperatures. This study provides evidence for huge functional complexes of β pore-forming toxins and emphasizes their potential variance in composition.
Insights
Most beta pore-forming toxins form large, functional complexes, not just the smaller SDS-resistant oligomers previously observed. These huge complexes, nearly 1 MDa, reveal the true nature of these cytocidal assemblages.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Beta pore-forming toxins require oligomerization to create membrane pores.
- The relationship between SDS-resistant oligomers and native functional toxin complexes remains unclear.
Purpose of the Study:
- To investigate the native structure of aerolysin-like toxin complexes.
- To determine if SDS-resistant oligomers accurately represent functional toxin assemblies.
Main Methods:
- Analysis of aerolysin, parasporin-2, and epsilon toxin oligomers with and without SDS.
- Utilizing Blue Native PAGE and size exclusion chromatography.
- Protease sensitivity assays on toxin complexes.
Main Results:
- Toxins formed large complexes (~1 MDa) in mild detergent, significantly larger than SDS-resistant oligomers (~200 kDa).
- Huge complexes showed partial protease sensitivity, suggesting a stable core.
- Intermediate complexes lacking SDS-resistant oligomers were observed at lower temperatures.
Conclusions:
- Beta pore-forming toxins assemble into large, functional complexes, challenging the significance of SDS-resistant oligomers alone.
- The composition of these large toxin complexes may be variable.
- This finding impacts understanding of toxin pore formation and cytocidal mechanisms.
Related Concept Videos
01:12Bacterial Toxins
02:41Protein Complex Assembly
Many viruses self-assemble into a fully functional unit using the infected host cell to...
01:19Formation of Lipopolysaccharides
01:57Protein Complexes with Interchangeable Parts
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order to...
01:18Assembly of Cytoskeletal Filaments
01:22Botulism