Crystallographic snapshots of sulfur insertion by lipoyl synthase

Martin I. McLaughlin, Nicholas D. Lanz, Peter J. Goldman, Kyung Hoon Lee, Squire J. Booker, Catherine L. Drennan

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Lipoyl synthase (LipA) catalyzes the insertion of two sulfur atoms at the unactivated C6 and C8 positions of a protein-bound octanoyl chain to produce the lipoyl cofactor. To activate its substrate for sulfur insertion, LipA uses a [4Fe-4S] cluster and S-adenosylmethionine (AdoMet) radical chemistry; the remainder of the reaction mechanism, especially the source of the sulfur, has been less clear. One controversial proposal involves the removal of sulfur from a second (auxiliary) [4Fe-4S] cluster on the enzyme, resulting in destruction of the cluster during each round of catalysis. Here, we present two high-resolution crystal structures of LipA from Mycobacterium tuberculosis: one in its resting state and one at an intermediate state during turnover. In the resting state, an auxiliary [4Fe-4S] cluster has an unusual serine ligation to one of the irons. After reaction with an octanoyllysine-containing 8-mer peptide substrate and 1 eq AdoMet, conditions that allow for the first sulfur insertion but not the second insertion, the serine ligand dissociates from the cluster, the iron ion is lost, and a sulfur atom that is still part of the cluster becomes covalently attached to C6 of the octanoyl substrate. This intermediate structure provides a clear picture of iron-sulfur cluster destruction in action, supporting the role of the auxiliary cluster as the sulfur source in the LipA reaction and describing a radical strategy for sulfur incorporation into completely unactivated substrates.

Original languageEnglish (US)
Pages (from-to)9446-9450
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number34
DOIs
StatePublished - Aug 23 2016

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Sulfur
Serine
Iron
S-Adenosylmethionine
Catalysis
Mycobacterium tuberculosis
Ligation
Ions
Ligands
Peptides
Enzymes

All Science Journal Classification (ASJC) codes

  • General

Cite this

McLaughlin, Martin I. ; Lanz, Nicholas D. ; Goldman, Peter J. ; Lee, Kyung Hoon ; Booker, Squire J. ; Drennan, Catherine L. / Crystallographic snapshots of sulfur insertion by lipoyl synthase. In: Proceedings of the National Academy of Sciences of the United States of America. 2016 ; Vol. 113, No. 34. pp. 9446-9450.
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Crystallographic snapshots of sulfur insertion by lipoyl synthase. / McLaughlin, Martin I.; Lanz, Nicholas D.; Goldman, Peter J.; Lee, Kyung Hoon; Booker, Squire J.; Drennan, Catherine L.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 113, No. 34, 23.08.2016, p. 9446-9450.

Research output: Contribution to journalArticle

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