5-Prime | Nonribosomal Peptide Synthesis
What is it? As the name suggests, nonribosomal peptide synthesis (NRPS) generates polypeptides sans ribosome. The resultant peptides, generally short oligomers of two to perhaps 48 residues, are not genome-encoded.
Where ribosomal translation is limited to the standard complement of 20 L-amino acids, nonribosomal peptides may contain unusual building blocks, including D-amino acids, methylated variants of the standard amino acids, and nonproteinogenic, hydroxylated, and glycosylated residues; more than 300 precursors are currently known. Sometimes the peptide products are hetero-cyclized, and the peptide backbone may be branched.
How are the peptides made? Nonribosomal peptides are created on massive, assembly line-like synthetases. These enzymes are modular, comprising a series of functional units that can bind a naked amino acid, activate it as a thioester, and couple it to the growing peptide chain. In linear NRPSs, the sequence of modules acts as the template that defines the resulting...