title: Predictive, structure-based model of amino acid recognition by nonribosomal peptide synthetase adenylation domains.
abstract: BACKGROUND
  Nonribosomal peptide synthetases (NRPSs) are large modular proteins that selectively bind, activate and condense amino acids in an ordered manner. Substrate recognition and activation occurs by reaction with ATP within the adenylation (A) domain of each module. Recently, the crystal structure of the A domain from the gramicidin synthetase (GrsA) with L-phenylalanine and adenosine monophosphate bound has been determined.
  
  
  RESULTS
  Critical residues in all known NRPS A domains have been identified that align with eight binding-pocket residues in the GrsA A domain and define sets of remarkably conserved recognition templates. Phylogenetic relationships among these sets and the likely specificity determinants for polar and nonpolar amino acids were determined in light of extensive published biochemical data for these enzymes. The binding specificity of greater than 80% of the known NRPS A domains has been correlated with more than 30 amino acid substrates.
  
  
  CONCLUSIONS
  The analysis presented allows the specificity of A domains of unknown function (e.g. from polymerase chain reaction amplification or genome sequencing) to be predicted. Furthermore, it provides a rational framework for altering of A domain specificity by site-directed mutagenesis, which has significant potential for engineering the biosynthesis of novel natural products.
authors.affiliation: Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, USA.
authors.forename: G L
authors.initials: GL
authors.lastname: Challis
authors.forename: J
authors.initials: J
authors.lastname: Ravel
authors.forename: C A
authors.initials: CA
authors.lastname: Townsend
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000378:metabolism; D001419:Bacteria / Q000201:enzymology / Q000235:genetics; D020134:Catalytic Domain / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D000591:Amino Acid Isomerases; C022343:phenylalanine racemase (ATP-hydrolyzing); D010453:Peptide Synthases