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Substrate specificity of Pasteurella multocida toxin for α subunits of heterotrimeric G proteins

Joachim H C Orth1, Ines Fester, Peter Siegert

  • 1Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany. joachim.orth@pharmakol.uni-freiburg.de

FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology
|November 15, 2012
PubMed

Insights

Pasteurella multocida toxin (PMT) activates G proteins by deamidating a key residue. This study reveals PMT targets three of four G protein families, clarifying its molecular mechanism and substrate specificity.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Toxicology

Background:

  • Pasteurella multocida toxin (PMT) is a key virulence factor.
  • PMT disrupts host cell signaling by targeting heterotrimeric G proteins.
  • Previous studies showed PMT deamidates Gα(i2), causing constitutive activation.

Purpose of the Study:

  • To investigate the specificity of PMT for its G-protein targets.
  • To elucidate the molecular and structural basis for PMT's substrate discrimination.

Main Methods:

  • Mass spectrometric analyses.
  • Utilized a monoclonal antibody specific for deamidated G proteins.
  • Employed G-protein fragments and chimeras to study structural basis.

Main Results:

  • PMT deamidates three out of four G protein families (Gα(q/11), Gα(i1,2,3), and Gα(12/13)).
  • Deamidation was observed in both mouse and human G proteins.
  • Catalytically inactive PMT mutant did not cause deamidation.
  • Structural basis for substrate discrimination was identified.

Conclusions:

  • PMT exhibits broad specificity for heterotrimeric G proteins.
  • The study elucidates the molecular mechanism of PMT's action.
  • Structural insights into G protein-toxin interactions were provided.

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