Lipoic acid is assembled on its cognate proteins (e.g. the E2 subunit of pyruvate dehydrogenase). An octanoyl moiety is transferred from the octanoyl-ACP of fatty acid synthetase to a specific lysine residue of the cognate protein followed by sulfur insertion at C6 and C8 of the octanoyl chain. The challenging chemistry of this last step is performed by the radical S-adenosylmethionine (SAM) enzyme lipoyl synthase (LipA). In this issue of the Biochemical Journal, Harmer et al. report the first crystal structure of a lipoyl synthase and demonstrate that it contains two [4Fe–4S] clusters, the canonical radical SAM cluster plus a second auxiliary cluster having an unprecedented serine ligand. The structure provides strong support for the model in which the auxiliary cluster donates the lipoate sulfur atoms.
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Commentary| October 23 2014
The structure of lipoyl synthase, a remarkable enzyme that performs the last step of an extraordinary biosynthetic pathway
John E. Cronan
John E. Cronan 1
*Departments of Microbiology and Biochemistry, University of Illinois, Urbana, IL 61801, U.S.A.
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Biochem J (2014) 464 (1): e1–e3.
August 15 2014
August 18 2014
A commentary has been published: Structures of lipoyl synthase reveal a compact active site for controlling sequential sulfur insertion reactions
John E. Cronan; The structure of lipoyl synthase, a remarkable enzyme that performs the last step of an extraordinary biosynthetic pathway. Biochem J 15 November 2014; 464 (1): e1–e3. doi: https://doi.org/10.1042/BJ20141061
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