A Radical Clock Probe Uncouples H Atom Abstraction from Thioether Cross-Link Formation by the Radical S-Adenosyl-l-methionine Enzyme SkfB.

ABSTRACT: Sporulation killing factor (SKF) is a ribosomally synthesized and post-translationally modified peptide (RiPP) produced by Bacillus. SKF contains a thioether cross-link between the α-carbon at position 40 and the thiol of Cys32, introduced by a member of the radical S-adenosyl-l-methionine (SAM) superfamily, SkfB. Radical SAM enzymes employ a 4Fe-4S cluster to bind and reductively cleave SAM to generate a 5'-deoxyadenosyl radical. SkfB utilizes this radical intermediate to abstract the α-H atom at Met40 to initiate cross-linking. In addition to the cluster that binds SAM, SkfB also has an auxiliary cluster, the function of which is not known. We demonstrate that a substrate analogue with a cyclopropylglycine (CPG) moiety replacing the wild-type Met40 side chain forgoes thioether cross-link

SUBMITTER: Kincannon WM 

PROVIDER: S-EPMC6094349 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature