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Small-angle X-ray solution scattering study on the dimerization of the FKBP25mem from Legionella pneumophila
B Schmidt1, S König, D Svergun
1Max-Planck-Gesellschaft, Arbeitsgruppe Enzymologie der Peptidbindung, Halle/Saale, Germany.
Abstract:
The dimerization of the FK506-binding peptidyl-prolyl cis/trans-isomerase (PPIase) FKBP25mem (Mip (macrophage infectivity potentiator) protein) from Legionella pneumophila was studied by small-angle X-ray solution scattering. A value of 44 kDa, independent on the protein concentration between 2 and 13 mg/ml, confirming that FKBP25mem is a dimer was found for the molecular mass of the protein. The radius of gyration of the protein is 3.3 nm and the Porod volume 87 nm3. A model of the shape of FKBP25mem was evaluated from the scattering curve. Each monomer consists of a proximal and a peripheral domain, which are perpendicular to each other. The envelope of the crystallographic model of human FKBP12 fits well into the peripheral domain. The contact regions between the two monomers in the dimeric protein are probably located between the N-terminal parts of the monomers.
Insights
The Legionella pneumophila FKBP25mem protein forms stable dimers, with each monomer featuring distinct proximal and peripheral domains. Structural analysis reveals potential N-terminal contact regions crucial for this dimeric complex.
Area of Science:
- Structural Biology
- Protein Biochemistry
- Microbiology
Background:
- FKBP25mem, a peptidyl-prolyl cis/trans-isomerase (PPIase) from Legionella pneumophila, also known as the macrophage infectivity potentiator (Mip) protein, is implicated in bacterial virulence.
- Understanding the quaternary structure of FKBP25mem is essential for elucidating its biological function and interactions within the host environment.
Purpose of the Study:
- To investigate the oligomeric state and solution structure of the Legionella pneumophila FKBP25mem protein.
- To determine the molecular mass, overall shape, and domain organization of FKBP25mem in solution.
Main Methods:
- Small-angle X-ray solution scattering (SAXS) was employed to study the dimerization and structural characteristics of FKBP25mem.
- Analysis of SAXS data yielded molecular mass, radius of gyration, and Porod volume, enabling shape modeling.
Main Results:
- FKBP25mem exists as a stable dimer with a molecular mass of 44 kDa, independent of protein concentration (2-13 mg/ml).
- The protein exhibits a radius of gyration of 3.3 nm and a Porod volume of 87 nm3.
- A structural model revealed that each monomer comprises perpendicular proximal and peripheral domains, with the peripheral domain accommodating a structure similar to human FKBP12.
Conclusions:
- FKBP25mem forms a stable dimeric complex, suggesting functional relevance for this quaternary structure.
- The dimeric structure features distinct domains, with potential inter-monomer contact sites located at the N-terminal regions.
- The structural insights provide a foundation for understanding FKBP25mem's role in Legionella pneumophila pathogenesis.