J. Biol. Chem., Vol. 262, Issue 3, 1060-1064, Jan, 1987

Dephosphorylation of phosphoproteins and synthetic phosphopeptides. Study of the specificity of the polycation-stimulated and MgATP- dependent phosphorylase phosphatases

P Agostinis, J Goris, E Waelkens, LA Pinna, F Marchiori and W Merlevede

The substrate specificity of different forms of polycation-stimulated (PCSH, PCSL, and PCSC) phosphorylase phosphatases and of the catalytic subunit of the MgATP-dependent protein phosphatase from rabbit skeletal muscle was investigated. This was done, with phosphorylase a as the reference substrate, using the synthetic phosphopeptides patterned after the phosphorylated sites of pyruvate kinase (type L) (Arg2-Ala- Ser(32P)-Val-Ala (S2), and its Thr(32P) substitute (T4)), inhibitor-1 (Arg4-Pro-Thr(32P)-Pro-Ala (T5), Arg2-Pro-Thr(32P)-Pro-Ala (T1), and its Ser(32P) substitute (S1)), and some modified phosphopeptides (Arg2- Ala-Thr(32P)-Pro-Ala (T2) and Arg2-Pro-Thr(32P)-Val-Ala (T3)), all phosphorylated by cyclic AMP-dependent protein kinase. In addition, casein(Thr-32P), phosphorylated by casein kinase-2, was also tested. The PCS phosphatases show a striking preference for the T4 configuration, PCSC being the least efficient. The catalytic subunit of the MgATP-dependent phosphatase was almost completely inactive toward all these substrates. As shown for the PCSH phosphatase, and comparing with T4, the two proline residues flanking the Thr(P) in T1 and T5, just as in inhibitor-1, drastically imparied the dephosphorylation by lowering the Vmax and not by affecting the apparent Km. The C-terminal proline (as in T2) by itself represents a highly unfavorable factor in the dephosphorylation. The critical effect of the sequence X-Thr(P)-Pro or Pro-Thr(P)-Pro (T1, T2, T5, and inhibitor-1) can be overcome by manganese ions. The additional finding that this is not the case with the Pro-Ser(P)-Pro sequence (S1) suggests that the effect of Mn2+ is highly substrate specific. These observations show the considerable importance of the primary structure of the substrate in determining the specificity of the protein phosphatases.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				K. A. Sheehan, Y. Ke, and R. J. Solaro p21-Activated kinase-1 and its role in integrated regulation of cardiac contractility Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2007; 293(3): R963 - R973. [Abstract] [Full Text] [PDF]

				P. Turowski, T. Myles, B. A. Hemmings, A. Fernandez, and N. J. C. Lamb Vimentin Dephosphorylation by Protein Phosphatase 2A Is Modulated by the Targeting Subunit B55 Mol. Biol. Cell, June 1, 1999; 10(6): 1997 - 2015. [Abstract] [Full Text]

				R. K. Freund and M. R. Palmer Beta Adrenergic Sensitization of gamma -Aminobutyric Acid Receptors to Ethanol Involves a Cyclic AMP/Protein Kinase A Second-Messenger Mechanism J. Pharmacol. Exp. Ther., March 1, 1997; 280(3): 1192 - 1200. [Abstract] [Full Text]