Download MendeleyPriming enzymes from the pikromycin synthase reveal how assembly-line ketosynthases catalyze carbon-carbon chemistry.
Dickinson, M.S., Miyazawa, T., McCool, R.S., Keatinge-Clay, A.T.(2022) Structure 30: 1331
- PubMed: 35738283
- DOI: https://doi.org/10.1016/j.str.2022.05.021
- Primary Citation of Related Structures:
7UWR, 8CZC - PubMed Abstract:
The first domain of modular polyketide synthases (PKSs) is most commonly a ketosynthase (KS)-like enzyme, KS Q , that primes polyketide synthesis. Unlike downstream KSs that fuse α-carboxyacyl groups to growing polyketide chains, it performs an extension-decoupled decarboxylation of these groups to generate primer units. When Pik127, a model triketide synthase constructed from modules of the pikromycin synthase, was studied by cryoelectron microscopy (cryo-EM), the dimeric didomain comprised of KS Q and the neighboring methylmalonyl-selective acyltransferase (AT) dominated the class averages and yielded structures at 2.5- and 2.8-Å resolution, respectively. Comparisons with ketosynthases complexed with their substrates revealed the conformation of the (2S)-methylmalonyl-S-phosphopantetheinyl portion of KS Q and KS substrates prior to decarboxylation. Point mutants of Pik127 probed the roles of residues in the KS Q active site, while an AT-swapped version of Pik127 demonstrated that KS Q can also decarboxylate malonyl groups. Mechanisms for how KS Q and KS domains catalyze carbon-carbon chemistry are proposed.
Organizational Affiliation:
Sauer Structural Biology Lab, The University of Texas at Austin, 102 E. 24th Street, Austin, TX 78712, USA.
