Exp Mol Med.  1997 Dec;29(4):229-233.

Phosphorylation of chicken protein tyrosine phosphatase 1 by casein kinase II in vitro

• Jung EJ
• Kang KR
• Kang YS

Abstract

The phosphorylation and dephosphorylation of proteins on tyrosyl residues are key regulatory mechanisms of cell growth and signal transduction and are controlled by opposing activities of protein tyrosine kinases and phosphotyrosyl phosphatases (PTPs). We have previously cloned and characterized a nontransmembrane chicken protein tyrosine phosphatase 1 (CPTP1) similar to human placental PTP1B (HPTP1B). CPTP1 contains several phosphorylation sequence motifs (S/T-X-X-D/E) for casein kinase II (CKII), [(I > E > V)-Y-(E > G)-(E > D > P > N)-(I/V > L)] for p56(1ck), and (P-E-S-P) for MAP kinase. To examine whether phosphatase activity of CPTP1 could be controlled by phosphorylation, CPTP1 and HPTP1B fusion proteins purified from E. coil were subjected to the in vitro phosphorylation by CKII. Phosphoamino acid analysis revealed that CPTP1 was phosphorylated on both serine and threonine residues by CKII in vitro. In addition, the degree of the phosphorylation of CPTP1 by CKII was shown to be five times higher than that of HPTP1B. Phosphorylation on both serine and threonine residues of CPTP1 in vitro results in an inhibition of its phosphatase activity. This result suggests that phosphorylation of CPTP1 and HPTP1B by CKII might be implicated in the regulation of their catalytic activities in the cell.

Keyword

chicken protein tyrosine phosphatase; casein kinase II

MeSH Terms

Casein Kinase II*
Casein Kinases*
Caseins*
Chickens*
Clone Cells
Humans
Phosphoric Monoester Hydrolases
Phosphorylation*
Phosphotransferases
Protein Tyrosine Phosphatases*
Protein-Tyrosine Kinases
Serine
Signal Transduction
Threonine
Casein Kinase II
Casein Kinases
Caseins
Phosphoric Monoester Hydrolases
Phosphotransferases
Protein Tyrosine Phosphatases
Protein-Tyrosine Kinases
Serine
Threonine