Characterization of a Radical Intermediate in Lipoyl Cofactor Biosynthesis

Nicholas D. Lanz, Justin M. Rectenwald, Bo Wang, Elizabeth S. Kakar, Tatiana N. Laremore, Squire J. Booker, Alexey Silakov

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Lipoyl synthase (LipA) catalyzes the final step in the biosynthesis of the lipoyl cofactor, the insertion of two sulfur atoms at C6 and C8 of an n-octanoyl chain. LipA is a member of the radical S-adenosylmethionine (SAM) superfamily of enzymes and uses two [4Fe-4S] clusters to catalyze its transformation. One cluster binds in contact with SAM and donates the requisite electron for the reductive cleavage of SAM to generate two 5′-deoxyadenosyl 5′-radicals, which abstract hydrogen atoms from C6 and C8 of the substrate. By contrast, the second, auxiliary [4Fe-4S] cluster, has been hypothesized to serve as the sulfur donor in the reaction. Such a sacrificial role for an iron-sulfur cluster during catalysis has not been universally accepted. Use of a conjugated 2,4-hexadienoyl-containing substrate analogue has allowed the substrate radical to be trapped and characterized by continuous-wave and pulsed electron paramagnetic resonance methods. Here we report the observation of a 57Fe hyperfine coupling interaction with the paramagnetic signal, which indicates that the iron-sulfur cluster of LipA and its substrate are within bonding distance.

Original languageEnglish (US)
Pages (from-to)13216-13219
Number of pages4
JournalJournal of the American Chemical Society
Volume137
Issue number41
DOIs
StatePublished - Oct 21 2015

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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