Unraveling the Biosynthesis of the Essential Lipoyl Cofactor in Staphylococcus aureus

Abstract

Staphylococcus aureus (S. aureus) is the leading cause of infections acquired in a hospital setting. In recent years, the rise and spread of methicillin‐resistant S. aureus (MRSA) that has evolved resistance to antibiotics previously successful at eradicating the infection has become a major global health concern. Thus, the search for novel antibiotic targets has been the focus of many research efforts. One potential new target is the biosynthesis of the lipoyl cofactor, which plays an essential role in the oxidative decarboxylation of various α‐keto acids and breakdown of glycine. The second step of the de novo pathway for the biosynthesis of the lipoyl cofactor, the attachment of two sulfur atoms to C6 and C8 of an n‐octanoyl chain connected to a target lysyl residue on a lipoyl carrier protein, is catalyzed by lipoyl synthase (LipA), a member of the radical S‐adenosylmethionine (SAM) superfamily. In addition to its [4Fe–4S] radical SAM cluster, LipA contains a second [4Fe–4S] ‘auxiliary cluster’ which is sacrificed during catalysis to supply the requisite sulfur atoms. The destruction of its auxiliary cluster renders LipA inactive in the absence of a system to restore it. Further studies have identified that Escherichia coli (E. coli) has an additional protein, NfuA, an iron‐sulfur cluster carrier protein, that can target LipA and regenerate its auxiliary cluster to reactivate it for catalysis. However, while E. coli LipA has been extensively studied, the S. aureus LipA homolog has not been fully characterized. Interestingly, in vitro studies have shown that the activity of S. aureus LipA is unaffected by S. aureus Nfu alone, indicating that a second factor may be involved. Recent in vivo studies have reported that an S. aureus protein, SufT, is involved in iron‐sulfur cluster assembly and is implicated in lipoic acid biosynthesis; however, the role of SufT is unknown. We will, therefore, use a combination of genetic, biochemical, and spectroscopic approaches to functionally characterize Staphylococcus aureus LipA and understand the potential roles of Staphylococcus aureus Nfu and SufT in the regeneration of LipA's auxiliary cluster. Ultimately, this information could be used to design antibiotics that target this pathway and obstruct the essential biosynthesis of lipoic acid, inducing death to pathogenic bacteria.Support or Funding InformationI acknowledge support from the HHMI EXROP program.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.