Modification of Isoaspartyl Peptides and Proteins by Protein Carboxyl Methyltransferase from Bovine Brain

  • Dana W. Aswad
  • Brett A. Johnson
  • Esther L. Langmack
  • Jill M. Shirokawa
Part of the Advances in Experimental Medicine and Biology book series (NATO ASI F, volume 231)


Recent findings indicate that protein carboxyl methyltransfer-ases (PCMTs) from mammalian brain and erythrocytes selectively and stoichiometrically methylate peptides and proteins which contain L-isoaspartyl (isoAsp) sites, i. e., aspartate which is linked via its side-chain β -carboxyl group, rather than via the typical α-carboxyl linkage (reviewed in reference 1). Why would an enzyme exhibit such an unusual specificity? As described below, we have undertaken several approaches to this question. First, we have explored the effect of sequence on the specificity of PCMT for isoAsp-containing peptides. Second, we have studied the effects of methylation on the structure and activity of isoAsp-containing peptides and proteins. Third, we have begun investigating possible sources of isoAsp under in vivo conditions. Our findings to date suggest that PCMT may play a role in the repair or degradation of isoAsp-bearing proteins which arise as a result of spontaneous deamidation of intrinsically labile asparagine sites.


Partial Repair Cyclic Imide Normal Peptide Methyl Acceptor Protein Carboxyl 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Aswad, D.W. and Johnson, B.A (1987) The unusual substrate specificity of eukaryotic protein carboxyl methyltransferases. Trends Biochem. Sci.12, 155–158CrossRefGoogle Scholar
  2. 2.
    Clarke, S. (1985) Protein carboxyl methyltransferases: two distinct classes of enzymes. Annu. Rev. Biochem.54, 479–506PubMedCrossRefGoogle Scholar
  3. 3.
    Paik, W.K. and Kim, S. (1980) in Protein Methylation, John Wiley and Sons, New YorkGoogle Scholar
  4. 4.
    Aswad, D.W. (1984) Stoichiometric methylation of porcine adreno-corticotropin by protein carboxyl methyltransferase requires deamidation of asparagine-25. J. Biol. Chem.259, 10714–10721PubMedGoogle Scholar
  5. 5.
    Bornstein, P. and Balian, G. (1977) Cleavage at Asn-Gly bonds with hydroxylamine. Methods. Enzymol.47, 132–145PubMedGoogle Scholar
  6. 6.
    Murray, E.D., Jr. and Clarke, S. (1984) Synthetic peptide substrates for the erythrocyte protein carboxyl methyltansferase. Detection of a new site of methylation at isomerized L-aspartyl residues. J. Biol. Chem.259, 10722–10732PubMedGoogle Scholar
  7. 7.
    Johnson, B.A., Murray, E.D., Jr., Clarke, S., Glass, D.B. and Aswad, D.W. (1987) Protein carboxyl methyltransferase facilitates conversion of atypical L-isoaspartyl peptides to normal L-aspartyl peptides. J. Biol. Chem.262, 5622–5629PubMedGoogle Scholar
  8. 8.
    McFadden, P.N. and Clarke, S. (1986) Chemical conversion of aspartyl peptides to isoaspartyl peptides. A method for generating new methyl-accepting substrates for the erythrocyte D-aspartyl/L-iso-aspartyl protein methyltransferase. J. Biol. Chem.261, 11503–11511PubMedGoogle Scholar
  9. 9.
    Lowenson, J. and Clarke, S. (1987) Protein carboxyl methyltransferase from human erythroxytes: substrate specificity with L-isoaspartyl and D-aspartyl-containing peptides and proteins. Fed. Proceed.46, 2090Google Scholar
  10. 10.
    Gagnon, C., Harbour, D. and Camato, R. (1984) Purification and characterization of protein methylesterase from rat kidney. J. Biol. Chem. 259, 10212–10215PubMedGoogle Scholar
  11. 11.
    Bernhard, S.A., Berger, A., Carter, J.H., Katchalski, E., Sela, M., and Shalitin, Y. (1962) Co-operative effects of functional groups in peptides. I. Aspartyl serine derivatives. J. Am. Chem. Soc. 84, 2421–2426CrossRefGoogle Scholar
  12. 12.
    Bodansky, M. and Kwei, J.Z. (1978) Side reactions in peptide synthesis. VI. A reexamination of the benzyl group in the protection of the side chains of tyrosine and aspartic acid. Int. J. Peptide Protein Res.12, 57–68CrossRefGoogle Scholar
  13. 13.
    Johnson, B.A. and Aswad, D.W. (1985) Enzymatic protein carboxyl methylation at physiological pH: cyclic imide formation explains rapid methyl turnover. Biochemistry 24, 2581–2586PubMedCrossRefGoogle Scholar
  14. 14.
    Murray, E.D., Jr. and Clarke, S. (1985) Metabolism of a synthetic L-isoaspartyl-containing hexapeptide in erythrocyte extracts. Enzymatic methyl esterification is followed by nonenzymatic succinimide formation. J. Biol. Chem. 261, 306–312Google Scholar
  15. 15.
    McFadden, P.N. and Clarke, S. (1987) Isoaspartyl peptides can be converted to aspartyl peptides by coupled enzymatic/nonenzymatic reactions: implications for the cellular repair of damaged proteins. Proc. Natl. Acad. Sci. USA 84, 2595–2599PubMedCrossRefGoogle Scholar
  16. 16.
    Johnson, B.A., Freitag, N.E. and Aswad, D.W. (1985) Protein carboxyl methyltransferase selectively modifies an atypical form of calmodulin. Evidence for methylation at deamidated asparagine residues. J. Biol. Chem.260, 10913–10916PubMedGoogle Scholar
  17. 17.
    Johnson, B.A., Langmack, E.L. and Aswad, D.W. (1987) Partial repair of deamidation-damaged calmodulin by protein carboxyl methyltransferase. J. Biol. Chem. in pressGoogle Scholar
  18. 18.
    Backer, J.M. and Dice, J.F. (1986) Covalent linkage of ribonuclease S-peptide to microinjected proteins causes their intracellular degradation to be enhanced during serum withdrawal. Proc. Natl. Acad. Sci. USA 83, 5830–5834PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1988

Authors and Affiliations

  • Dana W. Aswad
    • 1
  • Brett A. Johnson
    • 1
  • Esther L. Langmack
    • 1
  • Jill M. Shirokawa
    • 1
  1. 1.Department of PsychobiologyUniversity of California, IrvineIrvineUSA

Personalised recommendations