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Updated: Oct 26, 2025
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Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding
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Conformational changes of loops highlight a potential binding site in Rhodococcus equi VapB
Christina Geerds1, Albert Haas2, Hartmut H Niemann1
1Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany.
Summary
Virulence-associated proteins (Vaps) from Rhodococcus equi may bind ligands. A new VapB structure reveals a potential binding cavity, supporting the avidin-like binding hypothesis for Vaps.
Area of Science:
- Microbiology
- Structural Biology
- Protein Science
Background:
- Virulence-associated proteins (Vaps) are key to Rhodococcus equi pathogenicity.
- The precise function and mechanism of Vaps remain largely unknown.
- Vaps share a conserved β-barrel structure, but ligand-binding sites were not previously identified.
Purpose of the Study:
- To elucidate the structural basis for Vap function.
- To investigate the potential ligand-binding capabilities of Vaps.
- To resolve the structure of VapB in a novel crystalline form.
Main Methods:
- X-ray crystallography was employed to determine the structure of VapB.
- High-resolution (1.71 Å) structural analysis was performed.
- Comparative structural analysis with other Vap structures was conducted.
Main Results:
- A new crystal form of VapB revealed two molecules in the asymmetric unit.
- One VapB molecule exhibited a distinct loop conformation at the β-barrel apex.
- This conformational change created a hydrophobic cavity, suggesting a ligand-binding site.
Conclusions:
- The identified cavity in VapB supports its potential role as a ligand-binding protein.
- Structural similarities between Vaps and avidin further suggest a binding function.
- This finding advances the understanding of Vap mechanisms in Rhodococcus equi virulence.
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