Publication Abstract from PubMed
While the cis-acyltransferase modular polyketide synthase assembly lines have largely been structurally dissected, enzymes from within the recently discovered trans-acyltransferase polyketide synthase assembly lines are just starting to be observed crystallographically. Here we examine the ketoreductase (KR) from the first polyketide synthase module of the bacillaene nonribosomal peptide synthetase/polyketide synthase at 2.35-A resolution. This KR naturally reduces both alpha- and beta-keto groups and is the only KR known to do so during the biosynthesis of a polyketide. The isolated KR not only reduced an N-acetylcysteamine-bound beta-keto substrate to a D-beta-hydroxy product, but also an N-acetylcysteamine-bound alpha-keto substrate to an L-alpha-hydroxy product. That the substrates must enter the active site from opposite directions to generate these stereochemistries suggests that the acyl-phosphopantetheine moiety is capable of accessing very different conformations despite being anchored to a serine residue of a docked acyl carrier protein. The features enabling stereocontrolled alpha-ketoreduction may not be extensive since a KR that naturally reduces a beta-keto group within a cis-acyltransferase polyketide synthase was identified that performs a completely stereoselective reduction of the same alpha-keto substrate to generate the D-alpha-hydroxy product. A sequence analysis of trans-acyltransferase KRs reveals that a single residue, rather than a three-residue motif found in cis-acyltransferase KRs, is predictive of the orientation of the resulting beta-hydroxyl group.Proteins 2014. (c) 2014 Wiley Periodicals, Inc.
Structural and functional studies of a trans-acyltransferase polyketide assembly line enzyme that catalyzes stereoselective alpha- and beta-ketoreduction.,Piasecki SK, Zheng J, Axelrod AJ, E Detelich M, Keatinge-Clay AT Proteins. 2014 Mar 14. doi: 10.1002/prot.24561. PMID:24634061[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
