Structure-based drug discovery in the lipoic acid salvage pathway against MRSA

SCATTOLINI, A.; GRAMMATOGLO, K.; WINDSHÜGEL, B.; JIRGENSONS, A.; MANSILLA, M.C.

Mendoza

Congreso; Congreso de la Sociedad Argentina de Bioquímica y Biología molecular (SAIB); 2022

Sociedad Argentina de Bioquímica y Biología molecular

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of healthcare-related infection worldwide. 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 required for intermediary metabolism that is either synthesized de novo or acquired from environmental sources. 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. The bacterial pathogen S. aureus encodes the same enzymes required for de novo biosynthesis and salvage, but furthermore encodes two additional proteins, LplA2 and GcvH-L, that are sufficient for lipoic acid salvage during infection. 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 would be bound to E2s and recognized by anti-LA antibodies. These results indicate that, by the sequential action of lipoate ligase and amidotransferase, lpl-004 is accepted as a substrate and transferred to E2s, eventually impairing dehydrogenase activity as have been previously reported for selenolipoate in E. coli. This compound would be useful for further drug development against this pathogenic bacterium.