Probing the limits of interrupted adenylation domains by engineering a trifunctional enzyme capable of adenylation, N-, and S-methylation

Org Biomol Chem. 2019 Jan 31;17(5):1169-1175. doi: 10.1039/c8ob02996b.

Abstract

The adenylation (A) domains found in nonribosomal peptide synthetases (NRPSs) exhibit tremendous plasticity. Some A domains have been shown to display the ability to contain within them the catalytic portion of an auxiliary domain, most commonly that of a methyltransferase (M) enzyme. This unique feature of A domains interrupted by M domains allows them to possess bifunctionality, where they can both adenylate and methylate an amino acid substrate. Additionally, these types of inserted M domains are able to selectively carry out either backbone or side chain methylation of amino acids. Interruptions with M domains are naturally found to occur either between the a2-a3 or the a8-a9 of the ten conserved motifs of A domains. Herein, we set out to answer the following question: Can one A domain support two different M domain interruptions occurring in two different locations (a2-a3 and a8-a9) of the A domain and possess the ability to adenylate an amino acid and methylate it on both its side chain and backbone? To answer this question we added a backbone methylating M3S domain from TioS(A3aM3SA3b) between the a8-a9 region of a mono-interrupted A domain, TioN(AaMNAb), that already contained a side chain methylating MN domain between its a2-a3 region. We evaluated the di-interrupted A domain TioN(AMNAM3SA) with a series of radiometric and mass spectrometry assays and found that this engineered enzyme was indeed capable of all three activities. These findings show that production of an active trifunctional di-interrupted A domain is possible and represents an exciting new avenue for future nonribosomal peptide (NRP) derivatization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Monophosphate / chemistry*
  • Amino Acids / metabolism
  • Catalysis
  • Methylation
  • Methyltransferases / chemistry
  • Methyltransferases / isolation & purification
  • Methyltransferases / metabolism*
  • Peptide Synthases / chemistry
  • Peptide Synthases / isolation & purification
  • Peptide Synthases / metabolism*
  • Peptides / chemistry
  • Protein Domains
  • Protein Engineering*
  • Radiometry
  • Substrate Specificity
  • Tandem Mass Spectrometry

Substances

  • Amino Acids
  • Peptides
  • Adenosine Monophosphate
  • Methyltransferases
  • Peptide Synthases
  • non-ribosomal peptide synthase