The lipoic acid salvage pathway in Staphylococcus aureus is a promising target for antibacterial drugs

ALBERTINA SCATTOLINI; KONSTANTINOS GRAMMATOGLO; BJÖRN WINDSHÜGEL; AIGARS JIRGENSONS; MARÍA CECILIA MANSILLA

Praga

Congreso; 21st International Conference on Bacilli and Gram-Positive Bacteria; 2022

Infections with methicillin resistant Staphylococcus aureus are a global problem. The increasing emergence of multidrug resistant strains urgently requires novel therapeutic approaches in order to keep the drug discovery pipeline filled. Lipoic acid (LA) is a universally conserved sulfur-containing cofactor involved in one-carbon and oxidative metabolism. In Escherichia coli LA can be acquired by a salvage pathway, in which it is attached to lipoyl domains of GcvH, the H subunit of the glycine cleavage system, or the E2 subunits of dehydrogenase complexes by a lipoate ligase, LplA. Lipoate can also be de novo synthesized by a pathway requiring an octanoyltransferase and a lipoate synthase. We have characterized a more complex pathway in the model Gram-positive bacterium Bacillus subtilis, referred to as “lipoyl-relay”, that requires two additional proteins: GcvH and LipL, an amidotransferase. S. aureus contains two additional enzymes with presumptive roles in LA salvage during infection, LplA2 and GcvH-L. Due to its essentiality to cell viability and virulence, interfering with LA synthesis represents a promising approach for treating S. aureus infections. In this work, we performed a phenotypic screen of different molecules that were identified by a virtual screen against several S. aureus enzymes involved in LA salvage. One of the compounds caused a marked inhibition of the growth of the WT strain. This effect was lower in ΔlplA1 or ΔlplA2 single mutants, however the double mutant ΔlplA1 ΔlplA2 was able to grow in presence of the compound. Using protein extracts of different mutants of S. aureus, deficient in LA synthesis and uptake, we determined that lpl-004 is bound to E2s and recognized by anti-LA antibodies. These results indicate that, by the sequential action of lipoate ligases and amidotransferase, lpl-004 is accepted as a substrate and transferred to E2s, eventually impairing dehydrogenase activity. This compound would be useful for further drug development against this pathogenic bacterium.