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The post-translational modifications of Ral and Rac1 are important for the action of Ral-binding protein 1, a
K Matsubara1, T Hinoi, S Koyama
1Department of Biochemistry, Hiroshima University School of Medicine, Minami-ku, Japan.
FEBS Letters
|June 30, 1997
Summary
Post-translational modification of Ral is crucial for Ral-binding protein 1 (RalBP1) localization. RalBP1 activity on Rac1 and CDC42 is enhanced by their modifications, not Ral interaction.
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Ral-binding protein 1 (RalBP1) is an effector protein of Ral GTPase.
- RalBP1 exhibits GTPase-activating protein (GAP) activity towards Rac1 and CDC42.
- The influence of post-translational modifications on RalBP1 function is not fully understood.
Purpose of the Study:
- To investigate the role of post-translational modifications of Ral and Rac1 in RalBP1 action.
- To determine how Ral-RalBP1 interaction affects RalBP1's subcellular localization and enzymatic activity.
Main Methods:
- Expression of wild-type and mutant forms of Ral and Rac1 in COS cells.
- Subcellular fractionation to analyze protein localization.
- Co-expression experiments to study protein-protein interactions and functional effects.
- Assays to measure GTPase-activating activity.
Main Results:
- Post-translationally modified Ral(G23V) localized to the membrane, while unmodified Ral(G23V/C203S) remained in the cytosol.
- RalBP1 co-localized with membrane-bound Ral(G23V) but not with cytosolic Ral(G23V/C203S).
- RalBP1 showed enhanced GTPase-activating activity towards post-translationally modified Rac1 and CDC42.
Conclusions:
- Post-translational modification of Ral is essential for recruiting RalBP1 to the cell membrane.
- Ral-RalBP1 interaction is not required for RalBP1's GAP activity but facilitates its membrane localization.
- RalBP1 preferentially acts on modified forms of its substrates, Rac1 and CDC42.