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Structures of aminoarabinose transferase ArnT suggest a molecular basis for lipid A glycosylation

Vasileios I Petrou1, Carmen M Herrera2, Kathryn M Schultz3

  • 1Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.

Science (New York, N.Y.)
|February 26, 2016
PubMed

Insights

Structural insights into ArnT, an enzyme crucial for polymyxin resistance in Gram-negative bacteria, reveal how it modifies the bacterial outer membrane. Understanding this mechanism is key to developing new strategies against multidrug-resistant infections.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biochemistry

Background:

  • Polymyxins are critical last-resort antibiotics against Gram-negative bacteria.
  • Resistance to polymyxins involves modification of the bacterial outer membrane lipid A.
  • This modification is catalyzed by the enzyme 4-amino-4-deoxy-L-arabinose transferase (ArnT).

Purpose of the Study:

  • To elucidate the structural basis of ArnT activity.
  • To understand the mechanism of lipid substrate binding and catalysis by ArnT.
  • To provide a foundation for designing novel anti-infective strategies.

Main Methods:

  • X-ray crystallography of ArnT from Cupriavidus metallidurans.
  • Determination of crystal structures alone and in complex with undecaprenyl phosphate.
  • Functional mutagenesis studies informed by structural data.

Main Results:

  • Crystal structures of ArnT were determined at 2.8 and 3.2 angstrom resolution.
  • The structures revealed distinct cavities for lipidic substrates converging at the active site.
  • Undecaprenyl phosphate binding induces a structural rearrangement, stabilizing the active site for lipid A interaction.

Conclusions:

  • The structures provide a detailed mechanistic model for ArnT-mediated lipid A modification.
  • This work illuminates a key resistance mechanism against polymyxin antibiotics.
  • The findings offer potential targets for combating multidrug-resistant Gram-negative bacterial infections.

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