SDS22 selectively recognizes and traps metal-deficient inactive PP1
Meng S Choy1, Thomas M Moon1, Rini Ravindran2
1Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721.
Summary
The regulatory protein SDS22 binds a metal-deficient form of protein phosphatase 1 (PP1), trapping it in an inactive state. Metal loading is crucial for SDS22 to release PP1, revealing a new mechanism for enzyme regulation.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Protein phosphatase 1 (PP1) is a key metalloenzyme regulating over half of cellular dephosphorylation.
- SDS22 is a conserved regulatory protein with paradoxical roles as both an inhibitor and activator of PP1.
- Understanding SDS22's regulatory mechanism is crucial for comprehending PP1 function.
Purpose of the Study:
- To resolve the contradictory roles of SDS22 as a PP1 regulator.
- To elucidate the structural and mechanistic basis of SDS22-PP1 interaction.
- To investigate the role of metal ions in PP1 regulation by SDS22.
Main Methods:
- Integration of cellular assays, biophysical techniques, and X-ray crystallography.
- Characterization of SDS22 binding to specific PP1 conformations.
- Analysis of metal ion binding and dissociation dynamics.
Main Results:
- SDS22 selectively binds a unique, metal-deficient (M2-bound) conformation of PP1, inhibiting its activity.
- SDS22 traps PP1 by preventing the binding of the second essential metal ion (M1).
- Dissociation of SDS22 is coupled to M1 metal loading, while M1-deficient mutants are constitutively bound.
Conclusions:
- Metal ion loading and release are critical for PP1 regulation by SDS22.
- SDS22 acts as a dynamic regulator, controlling PP1 activity through metal-dependent complex formation and dissociation.
- These findings have significant implications for PP1 maturation, activity modulation, and holoenzyme assembly.
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