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Interactions between bacterial flagellar axial proteins in their monomeric state in solution
Yukio Furukawa1, Katsumi Imada, Ferenc Vonderviszt
1Protonic NanoMachine Project, ERATO, JST, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan.
Journal of Molecular Biology
|June 11, 2002
Summary
Bacterial flagellum assembly involves specific protein interactions. Researchers found flagellin promotes HAP3 aggregation and HAP3 forms heterodimers with HAP2, revealing key insights into flagellar structure.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- The bacterial flagellum's axial structure comprises multiple proteins like hook protein and flagellin.
- These proteins typically remain monomeric in solution to prevent premature self-assembly.
- Systematic studies on interactions between monomeric axial proteins are lacking.
Purpose of the Study:
- To investigate self and cross-association between hook protein, flagellin, and hook-associated proteins (HAP1, HAP2, HAP3).
- To understand the solution behavior of these proteins and their potential interactions.
Main Methods:
- Gel-filtration chromatography
- Analytical ultracentrifugation
- Studied all possible pairwise associations between hook protein, flagellin, HAP1, HAP2, and HAP3.
Main Results:
- Flagellin induced HAP3 aggregation into beta-amyloid-like filaments without stable binding.
- HAP3 addition caused disassembly of HAP2 decamers, forming stable HAP2-HAP3 heterodimers.
- HAP2 terminal regions are crucial for heterodimer formation, while HAP3 terminal regions are not, indicating interaction polarity.
Conclusions:
- Specific interactions between flagellar axial proteins occur in solution.
- HAP3 and HAP2 form stable heterodimers, mirroring their interactions in the flagellar structure.
- Findings provide insights into the assembly mechanism of the bacterial flagellum.