Evolutionary repurposing of a metabolic thiolase complex enables antibiotic biosynthesis
Abstract
The functional diversification of biosynthetic enzymes underlies the chemical richness of natural products, yet how primary metabolic enzymes evolve to acquire specialized functions in secondary metabolism remains elusive. Here, we report a tripartite enzyme complex from oral Streptococcus species—comprising 3-hydroxy-3-methylglutaryl (HMG)-CoA synthase (HMGS), acetyl-CoA acetyltransferase (ACAT), and a DUF35 protein—that catalyzes an unusual Friedel–Crafts C-acetylation on a pyrrolidine-2,4-dione scaffold, completing the biosynthesis of the antibiotic reutericyclin A. Cryo-electron microscopy of the S. macacae-derived thiolase complex (SmaATase) reveals a conserved architecture resembling the archaeal HMGS/ACAT/DUF35 complex involved in the mevalonate pathway, yet with key catalytic residues rewired to enable novel substrate specificity. Biochemical characterization, molecular modeling, and evolutionary analysis confirmed that the ancestral activity of HMG-CoA synthesis has been lost, while the complex has been repurposed to mediate Friedel–Crafts C-acylation of small molecule acceptors. These findings reveal a rare example of thiolase complex neofunctionalization, shedding light on an underexplored trajectory in enzyme evolution and offering a template for engineering C–C bond-forming catalysts in synthetic biology.
Metrics
DOI:
Submission ID:
Downloads
Posted
How to Cite
Declaration of Competing Interests
The authors declare no competing interests to disclose.
Copyright
The copyright holder for this preprint is the author/funder.
All rights reserved. This work is protected by copyright. No part of this work may be reproduced, distributed, or transmitted in any form or by any means without the prior written permission of the copyright holder.