Related Experiment Videos
Protein phosphatase type 1 catalytic subunit forms nondissociable dimers
1Brown University, Division of Biology and Medicine, Providence, Rhode Island 02912.
Archives of Biochemistry and Biophysics
|November 15, 1989
Summary
Protein phosphatase type 1 exists as both a 38,000 Da monomer and a 70,000 Da dimer. This dimer forms spontaneously and is resistant to dissociation, impacting protein phosphatase type 1 regulation.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Protein phosphatase type 1 (PP1) is crucial for dephosphorylating phosphoproteins in skeletal muscle and liver.
- The active catalytic subunit of PP1 is typically 36-38 kDa, but a 70 kDa form has also been reported.
Purpose of the Study:
- To investigate the discrepancy in reported molecular weights for protein phosphatase type 1.
- To characterize the relationship between the 38 kDa and 70 kDa forms of PP1.
Main Methods:
- Mono Q chromatography for protein separation.
- Western immunoblotting with specific antibodies.
- Cyanogen bromide cleavage and peptide mapping.
- Reversed-phase high-performance liquid chromatography (RP-HPLC).
- Amino acid composition analysis.
Main Results:
- Both 38 kDa and 70 kDa proteins were purified from rabbit skeletal muscle.
- Antibodies against the catalytic fragment recognized both proteins.
- Peptide mapping and amino acid analysis confirmed both proteins are identical.
- The 38 kDa catalytic subunit spontaneously forms a stable 70 kDa dimer.
- This dimer resists standard dissociation but can be cleaved by proteases.
Conclusions:
- The 70 kDa protein is a non-dissociable dimer of the 38 kDa catalytic subunit of protein phosphatase type 1.
- Dimer formation is a spontaneous process and may be regulated.
- Changes in dimer levels reflect physiological alterations in protein phosphatase type 1 activity.