Interdomain and Intermodule Organization in Epimerization Domain Containing Nonribosomal Peptide Synthetases.
Chen, W.H., Li, K., Guntaka, N.S., Bruner, S.D.(2016) ACS Chem Biol 11: 2293-2303
- PubMed: 27294598 
- DOI: https://doi.org/10.1021/acschembio.6b00332
- Primary Citation of Related Structures:  
5ISW, 5ISX - PubMed Abstract: 
Nonribosomal peptide synthetases are large, complex multidomain enzymes responsible for the biosynthesis of a wide range of peptidic natural products. Inherent to synthetase chemistry is the thioester templated mechanism that relies on protein/protein interactions and interdomain dynamics. Several questions related to structure and mechanism remain to be addressed, including the incorporation of accessory domains and intermodule interactions. The inclusion of nonproteinogenic d-amino acids into peptide frameworks is a common and important modification for bioactive nonribosomal peptides. Epimerization domains, embedded in nonribosomal peptide synthetases assembly lines, catalyze the l- to d-amino acid conversion. Here we report the structure of the epimerization domain/peptidyl carrier protein didomain construct from the first module of the cyclic peptide antibiotic gramicidin synthetase. Both holo (phosphopantethiene post-translationally modified) and apo structures were determined, each representing catalytically relevant conformations of the two domains. The structures provide insight into domain-domain recognition, substrate delivery during the assembly line process, in addition to the structural organization of homologous condensation domains, canonical players in all synthetase modules.
Organizational Affiliation: 
Department of Chemistry, University of Florida , P.O. Box 117200, Gainesville, Florida 32611, United States.