Giardia duodenalis 14-3-3 protein is polyglycylated by a tubulin tyrosine ligase-like member and deglycylated by two metallocarboxypeptidases

J Biol Chem. 2011 Feb 11;286(6):4471-84. doi: 10.1074/jbc.M110.181511. Epub 2010 Dec 6.


The flagellated protozoan Giardia duodenalis is a parasite of the upper part of the small intestine of mammals, including humans, and an interesting biological model. Giardia harbors a single 14-3-3 isoform, a multifunctional protein family, that is modified at the C terminus by polyglycylation, an unusual post-translational modification consisting of the covalent addition of one or multiple glycines on the γ-carboxyl groups of specific glutamic acids. Polyglycylation affects the intracellular localization of g14-3-3, as the shortening of the polyglycine chain is correlated with a partial relocalization of 14-3-3 inside the nuclei during encystation. In this work we demonstrate that the gTTLL3, a member of the tubulin tyrosine ligase-like family, is the enzyme responsible for the 14-3-3 polyglycylation. We also identify two metallopeptidases of the M20 family, here termed gDIP1 (giardial dipeptidase 1) and gDIP2, as enzymes able to shorten the g14-3-3 polyglycine tail both in vivo and in vitro. Finally, we show that the ectopic expression of gDIP2 alters the g14-3-3 localization and strongly hampers the cyst formation. In conclusion, we have identified a polyglycylase and two deglycylases that act in concert to modulate the stage-dependent glycylation status of the multifunctional regulatory g14-3-3 protein in G. duodenalis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins / genetics
  • 14-3-3 Proteins / metabolism*
  • Animals
  • Carboxypeptidases / genetics
  • Carboxypeptidases / metabolism*
  • Giardia / genetics
  • Giardia / metabolism*
  • Glycine / genetics
  • Glycine / metabolism
  • Metalloproteases / genetics
  • Metalloproteases / metabolism*
  • Metalloproteases / physiology*
  • Peptide Synthases / genetics
  • Peptide Synthases / metabolism*
  • Protein Processing, Post-Translational
  • Protein Structure, Tertiary
  • Protozoan Proteins / genetics
  • Protozoan Proteins / metabolism*


  • 14-3-3 Proteins
  • Protozoan Proteins
  • Carboxypeptidases
  • Metalloproteases
  • Peptide Synthases
  • tubulin polyglutamylase
  • Glycine