Modulation of type-1 protein phosphatase by synthetic peptides corresponding to the carboxyl terminus.
Protein phosphatase type-1 (PP-1) has a protease resistant catalytic core Mr = 35,000 (PP-35K) and carboxyl terminal segment which affects activity with various substrates. We found that micromolar concentration of a synthetic peptide, corresponding to residues 312-326 of the PP-1 carboxyl terminus (P312-326) that is missing from PP-35K, increased the phosphatase activity of PP-35K with phosphorylase and myosin light chains as substrates by decreasing the apparent Km without a change in Vm. Purified PP-1 and PP-35K were inhibited identically by okadaic acid, but peptide P312-326 only stimulated the activity of PP-35K, not full-length PP-1. Other peptides corresponding to the carboxyl terminus of phosphatase-2A or to the amino terminus of PP-1 did not affect the activity of PP-35K. A sequence conserved in PP-1 from different species, Pro-Ile-Thr-Pro-Pro was implicated as the active region because a derivative peptide, Ala-Pro-Ile-Thr-Pro-Pro-Ala, stimulated the activity of PP-35K to the same extent as peptide P312-326 although at higher concentrations. These results indicate that the carboxyl terminus of PP-1 interacts with the catalytic core to modulate its activity, and suggest that the physiological regulation of PP-1 may involve this segment.
Martin
B L
BL
Section of Biochemistry, Brown University, Providence, RI 02912.
Shriner
C L
CL
Brautigan
D L
DL
D000595:Amino Acid Sequence; D001665:Binding Sites; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D004988:Ethers, Cyclic / Q000494:pharmacology; D015151:Immunoblotting; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009218:Myosins / Q000378:metabolism; D019319:Okadaic Acid; D010446:Peptide Fragments / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D054648:Protein Phosphatase 2; D013379:Substrate Specificity
D004988:Ethers, Cyclic; D046911:Macromolecular Substances; D010446:Peptide Fragments; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D009218:Myosins