The cluster of penicillin biosynthetic genes. Identification and characterization of the pcbAB gene encoding the alpha-aminoadipyl-cysteinyl-valine synthetase and linkage to the pcbC and penDE genes.

Modular Peptide Synthetases Involved in Nonribosomal Peptide Synthesis

“…A region of about 250 amino acid residues located to the C-terminal end of bacterial modules that are involved in adding the last amino acid to the linear peptides (Figure and , pink color in following modules: ACV-Val, GrsB-Leu, SrfA-C-Leu, TycC-Leu, and BacC-Asn) exhibits homology to thioesterases. ,− ,,,, This region is referred to as the thioesterase domain (TE domain). It has been found in the same location in the bacterial operons encoding multifunctional enzymes for the synthesis of the ACV tripeptide, ,,, bacitracin, enterobactin, gramicidin S, pyoverdine, surfactin, and tyrocidine 41 which are of bacterial and fungal origin. Due to its location, it is tempting to speculate that the TE domain is involved in hydrolytic cleavage of the linear peptide products, i.e., termination of nonribosomal peptide biosynthesis.…”

“…29,[31][32][33]41,42,119,120 This region is referred to as the thioesterase domain (TE domain). It has been found in the same location in the bacterial operons encoding multifunctional enzymes for the synthesis of the ACV tripeptide, 29,31,119,120 bacitracin, 42 enterobactin, 107 gramicidin S, 32 pyoverdine, 39 surfactin, 33 and tyrocidine 41 which are of bacterial and fungal origin. Due to its location, it is tempting to speculate that the TE domain is involved in hydrolytic cleavage of the linear peptide products, i.e., termination of nonribosomal peptide biosynthesis.…”

The Mechanism of ACV Synthetase

“…The power of modern DNA sequencing methodology has been demonstrated by the efficiency with which several groups were able to establish the inferred primary structure of ACV synthetase and even larger peptide synthetases. The calculated molecular masses of ACV synthetase from the inferred primary translation products from several sources are therefore as follows: from A. nidulans molecular mass 422 428 Da, 3 770 residues; from C. acremonium molecular mass 414 767 Da, 3 712 residues; from Nocardia lactamdurans molecular mass 404 079 Da, 3 649 residues; from P. chrysogenum two slightly variant sequences giving molecular masses of 421 068 Da, 3 746 residues and 425 914 Da, 3 791 residues. , Clearly the molecular masses of the inferred primary translation products are much more consistent than estimates of the molecular mass of the isolated enzymes, although as noted in section III there might be significant differences caused by post-translational processing or artifactual degradation during isolation. The inferred primary structures show a number of features in common with other peptide synthetases.…”

“…The inferred primary structures show a number of features in common with other peptide synthetases. The sequence reveals a 3-fold internal homology with three distinct domains, A, B, and C. − The other peptide synthetases are also comprised of very similar concatenenated homologous domains, typically one for each of the amino acids in the peptide product of the enzyme. It was therefore proposed that these structural repeats correspond to the functional entities responsible for the activation and incorporation of each amino acid substrate into the growing peptide chain.…”

Structural insights into nonribosomal peptide enzymatic assembly lines

“…The erythromycin or 6-deoxyerythronolide B synthase (DEBS) has seven modules spread over three protein subunits and this multimodular assembly line is termed a type I PKS. 20,21 The most common architecture of NRP synthetase assembly lines is the type I pattern, exemplified by (a) aminoadipyl-cysteinyl-valine synthetase, 22,23 a three module, ten domain 480 kDa single subunit enzyme that carries out the first committed step in penicillin biosynthesis, and (b) the seven module vancomycin synthetase, organized in a 3 module, 3 module, 1 module assembly of three subunit proteins. 24,25 Following two decades of intensive investigation of the chemical mechanisms of PKS and NRPS assembly lines, the chemical logic is fairly well deciphered.…”