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Structural insights into the GTPase domain of Escherichia coli MnmE protein

Daniel Monleón1, Marta Martínez-Vicente, Vicent Esteve

  • 1Department of Physical Chemistry, University of Valencia, C/Dr. Moliner, 50, Burjassot 46100 Valencia, Spain.

Proteins
|December 5, 2006
PubMed

Insights

The Escherichia coli MnmE protein, crucial for tRNA modification, requires GTP hydrolysis for function. Its G-domain structure reveals a unique catalytic mechanism distinct from other GTPases, potentially impacting mitochondrial disease research.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Structural Biology

Background:

  • Escherichia coli MnmE protein is a GTPase involved in tRNA modification.
  • Eukaryotic MnmE homologues are vital for mitochondrial respiration, suggesting a role in mitochondrial diseases.
  • MnmE requires efficient GTP hydrolysis, not just binding, for functional activity.

Purpose of the Study:

  • To investigate the GTP hydrolysis mechanism of the MnmE protein.
  • To explore the effect of low pH on GTP binding, hydrolysis, and transition state mimic formation.
  • To determine the structure of the MnmE G-domain using nuclear magnetic resonance (NMR).

Main Methods:

  • Analysis of GTP binding and hydrolysis under varying pH conditions.
  • Formation and analysis of a MnmE transition state mimic.
  • Nuclear magnetic resonance (NMR) spectroscopy for structural determination of the MnmE G-domain.
  • Integration of NMR restraints with homology modeling for structure refinement.

Main Results:

  • GTP hydrolysis by MnmE is impaired at acidic pH, while GTP binding and transition state mimic formation are not significantly affected.
  • This suggests a difference between the transition state mimic and the true transition state, with key residues affected by low pH.
  • The MnmE G-domain structure was determined, revealing it lacks the typical arginine finger motif found in other GTPases.
  • Arg252 may contribute to transition state stabilization.

Conclusions:

  • MnmE utilizes a unique catalytic mechanism for GTP hydrolysis, differing from canonical arginine-finger dependent GTPases.
  • The findings provide structural insights into MnmE function and its potential role in mitochondrial health and disease.
  • Further research into MnmE's mechanism could inform therapeutic strategies for mitochondrial disorders.

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