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Solution structure of the human signaling protein RACK1
Kaliandra A Gonçalves1, Julio C Borges, Julio C Silva
1Laboratório Nacional de Biociências (LNBio), Centro de Pesquisa em Energia e Materiais (CNPEM), Campinas, SP, Brazil.
BMC Structural Biology
|June 10, 2010
Summary
Receptor of activated kinase 1 (RACK1) is mainly a monomer in solution, as shown by biophysical analysis. Human RACK1 strongly interacts with Ki-1/57, indicating a significant protein-protein interaction relevant to cellular processes.
Area of Science:
- Biophysics
- Molecular Biology
- Structural Biology
Background:
- Receptor of activated kinase 1 (RACK1) is an adaptor protein involved in diverse cellular functions.
- RACK1 is known to mediate protein-protein interactions through its seven WD repeats.
- Its roles span protein translation, neuropathology, cellular stress, and tissue development.
Purpose of the Study:
- To determine the low-resolution structure of human RACK1 in solution.
- To investigate the oligomeric state and biophysical properties of RACK1.
- To analyze the interaction between RACK1 and Ki-1/57.
Main Methods:
- Small-angle X-ray scattering (SAXS) for structural analysis.
- Sedimentation velocity and equilibrium analytical ultracentrifugation for oligomeric state and molecular weight determination.
- Fluorescence spectroscopy and sedimentation equilibrium to study RACK1-Ki-1/57 interaction.
Main Results:
- Human RACK1 is predominantly globular and monomeric in solution, with a shape slightly asymmetric.
- SAXS data revealed structural similarity to homology and crystallographic models.
- RACK1 interacts with Ki-1/57(122-413) with a 1:1 stoichiometry, a strong binding affinity (KD of 0.7 x 10(-6) M), and potentially cooperatively.
Conclusions:
- RACK1 exists primarily as a monomer in solution, confirmed by SAXS and ultracentrifugation.
- RACK1 and Ki-1/57(122-413) exhibit strong binding under the experimental conditions.
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