Evidence for a novel phosphopantetheinyl transferase domain in the polyketide synthase for enediyne biosynthesis

Abstract 

The polyketide synthase associated with the biosynthesis of enediyne-containing calicheamicin contains a putative phosphopantetheinyl transferase (PPTase) domain. By cloning and expressing the C-terminal region of the polyketide synthase and in vitro phosphopantetheinylation assay, we found that the PPTase domain exhibits preferred substrate specificity towards acyl and peptidyl carrier proteins in fatty acid and non-ribosomal peptide synthesis over its cognate partner. We also found evidence suggesting that the PPTase domain adopts a pseudo-trimeric structure, distinct from the pseudo-dimeric structure of type II PPTases. The results revealed a novel type of PPTase with unique structure and substrate specificity, and suggested that the polyketide synthase probably acquired the PPTase domain from a primary metabolic pathway in evolution.

Abbreviations: PPTase, phosphopantetheinyl transferase, CP, carrier protein, ACP, acyl carrier protein, PCP, peptidyl carrier protein, PKS, polyketide synthase, NRPS, non-ribosomal peptide synthase, FAS, fatty acid synthase, AcpS, acyl carrier protein synthase, DACP, ACP domain from the modular PKS DEBS, EACP, ACP from E. coli fatty acid synthesis pathway, meACP, ACP domain of the iterative PKS in calicheamicin biosynthesis (M. echinospora ssp.), GPCP, PCP domain of non-ribosomal peptide synthase (GrsA B. brevis)

Keywords: Phosphopantetheinyl transferase, Acyl carrier protein, Polyketide synthase, Enediyne, Calicheamicin