Review
Structure and function of the low Mr phosphotyrosine protein phosphatases

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Abstract

Phosphotyrosine protein phosphatases (PTPases) catalyse the hydrolysis of phosphotyrosine residues in proteins and are hence implicated in the complex mechanism of the control of cell proliferation and differentiation. The low Mr PTPases are a group of soluble PTPases displaying a reduced molecular mass; in addition, a group of low molecular mass dual specificity (ds)PTPases which hydrolyse phosphotyrosine and phosphoserine/threonine residues in proteins are known. The enzymes belonging to the two groups are unrelated to each other and to other PTPase classes except for the presence of a CXXXXXRS/T sequence motif containing some of the catalytic residues (active site signature) and for the common catalytic mechanism, clearly indicating convergent evolution. The low Mr PTPases have a long evolutionary history since microbial (prokaryotic and eukaryotic) counterparts of both tyrosine-specific and dsPTPases have been described. Despite the relevant number of data reported on the structural and catalytic features of a number of low Mr PTPases, only limited information is presently available on the substrate specificity and the true biological roles of these enzymes, in prokaryotic, yeast and eukaryotic cells.

Section snippets

Overview

Formation and hydrolysis of phosphate esters are among the most important reactions carried out by cells. These reactions are involved in a lot of biochemical activities such as polymerisation and expression of genetic material, biological membrane functioning, interactions between macromolecules, signal transduction and substrate activation in many biosynthetic pathways. Formation and hydrolysis of phosphate monoesters in proteins, mostly at the serine, threonine (the only known phosphorylated

Occurrence

Low Mr PTPases (EC 3.1.3.48) were initially studied as low Mr soluble acid phosphatases (EC 3.1.3.2) due to their hydrolytic activity on phosphate esters and in particular on p-nitrophenylphosphate (pNPP). However, they are not inhibited by the classical inhibitors of either acid phosphatases (tartrate) or phosphoserine/threonine protein phosphatases (EDTA, fluoride, okadaic acid) 69, 70; instead, they are specifically inhibited by micromolar Zn2+ and vanadate, as well as by phenylarsine oxide

Biological activity

Similarly to the other PTPases, neither the true biological substrates of the low Mr PTPases are known nor the way they interact with other proteins in cells and their biological significance are well understood. Nevertheless, a number of data on this topic have been reported since 1989, when the efficient dephosphorylation in vitro of the autophosphorylated EGF receptor by the bovine liver IF2 was shown [99]; successively, this finding has been confirmed in brain in vivo [100]and the

Structure

At present, the genes or amino acid sequences of a number of low Mr PTPases are known, together with the three-dimensional structure of one of these proteins. Bovine liver IF2 was the first low Mr PTPase sequenced [115]. The protein consists of 157 amino acid residues (Mr 17 953), is N-acetylated and contains eight cysteines (all in the reduced form). The enzyme does not show any sequence homology with alkaline or acid phosphatases nor with the phosphothreonine/serine protein phosphatases. No

Substrate specificity and catalytic mechanism

Poor information is currently available on the substrate specificity and physiological substrates of the low Mr PTPases (as is also the case of most other PTPases). A number of studies have been carried out by the use of both dominant negative mutants and Tyr-phosphorylated synthetic peptides with sequences corresponding to those around phosphorylation sites of receptor and non-receptor proteins as model substrates. From these and other studies a number of possible physiological substrates and

Low Mr dual specificity PTPases

Dual specificity (ds) PTPases are an emerging class of enzymes able to hydrolyse both phosphotyrosine and phosphoserine/threonine residues in proteins, whose number is progressively increasing. Some dsPTPases display a reduced molecular mass, similar to that shown by the low Mr PTPases; all dsPTPases show sequence homology to each other but are structurally distinct from the low Mr PTPases, both groups sharing only the active site signature common to all PTPases and the catalytic mechanism. A

Concluding remarks

A group of tyrosine-specific and some dual specificity PTPases are characterised by reduced molecular masses; the latter enzymes are able to dephosphorylate substrates containing phosphotyrosine and phosphoserine/threonine residues in close proximity. Tyr-specific and ds low Mr PTPases share no sequence homology with each other outside the active site signature, though apparently acting with the same kinetic mechanism; this is also identical to that displayed by the other PTPase classes,

Acknowledgements

The authors thank Dr. N. Taddei for his skillful review of the manuscript. Work from our laboratory was supported, in part, by grants from Italian MURST (40% and 60%) CNR (Target Project on Biotechnology and Bioinstrumentation, Target Project on Peptidi Bioattivi and from the Italian Association for Cancer Research (AIRC).

References (179)

  • J.B. Stock et al.

    J. Biol. Chem.

    (1992)
  • Y.-F. Wei et al.

    Arch. Biochem. Biophys.

    (1989)
  • B.T. Wakim et al.

    J. Biol. Chem.

    (1994)
  • H. Ohmori et al.

    J. Biol. Chem.

    (1993)
  • Y. Kim et al.

    J. Biol. Chem.

    (1993)
  • E.E. Kim et al.

    J. Mol. Biol.

    (1991)
  • P. Cohen et al.

    J. Biol. Chem.

    (1989)
  • P.T.W. Cohen et al.

    FEBS Lett.

    (1990)
  • B.L. Martin et al.

    J. Biol. Chem.

    (1986)
  • S.Q. Zhuo et al.

    J. Biol. Chem.

    (1994)
  • T. Hunter

    Cell

    (1995)
  • J.M. Bishop

    Cell

    (1991)
  • A. Ullrich et al.

    Cell

    (1990)
  • T. Hunter

    Cell

    (1987)
  • G. Daum et al.

    Trends Biochem. Sci.

    (1994)
  • R.J. Davis

    Trends Biochem. Sci.

    (1994)
  • D.A. Pot et al.

    Biochim. Biophys. Acta

    (1992)
  • H. Sun et al.

    Trends Biochem. Sci.

    (1994)
  • T. Hunter

    Cell

    (1989)
  • L.D. Shultz et al.

    Cell

    (1993)
  • L.A. Perkins et al.

    Cell

    (1992)
  • J.T. Pingel et al.

    Cell

    (1989)
  • K.L. Guan et al.

    J. Biol. Chem.

    (1991)
  • G. Carpenter et al.

    J. Biol. Chem.

    (1979)
  • N.K. Tonks et al.

    J. Biol. Chem.

    (1988)
  • R.L. Stone et al.

    J. Biol. Chem.

    (1994)
  • L.J. Mauro et al.

    Trends Biochem. Sci.

    (1994)
  • D.R. Alessi et al.

    Curr. Biol.

    (1995)
  • H. Sun et al.

    Cell

    (1993)
  • J. Pines

    Trends Biochem. Sci.

    (1994)
  • K. Galaktionov et al.

    Cell

    (1991)
  • W.G. Dunphy et al.

    Cell

    (1991)
  • S.M. Keyse

    Biochim. Biophys. Acta

    (1995)
  • G. Ramponi et al.

    Int. J. Biochem. Cell Biol.

    (1997)
  • R.L. Heinrikson

    J. Biol. Chem.

    (1969)
  • J. Chernoff et al.

    Arch. Biochem. Biophys.

    (1985)
  • D.L. Brautigan et al.

    Methods Enzymol.

    (1988)
  • J. Gordon

    Methods Enzymol.

    (1991)
  • C. Baldijao et al.

    Biochim. Biophys. Acta

    (1975)
  • J. Dissing et al.

    Biochim. Biophys. Acta

    (1979)
  • G.L. Lawrence et al.

    Arch. Biochem. Biophys.

    (1981)
  • E.M. Taga et al.

    Arch. Biochem. Biophys.

    (1982)
  • Z.Y. Zhang et al.

    Arch. Biochem. Biophys.

    (1990)
  • J. Dissing et al.

    Biochim. Biophys. Acta

    (1990)
  • J. Dissing et al.

    J. Biol. Chem.

    (1991)
  • P. Cirri et al.

    J. Biol. Chem.

    (1996)
  • Y.-Y.P. Wo et al.

    J. Biol. Chem.

    (1992)
  • M. Potts et al.

    J. Biol. Chem.

    (1993)
  • S.M. Wilbanks et al.

    J. Biol. Chem.

    (1993)
  • O. Mondesert et al.

    J. Biol. Chem.

    (1994)
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