Acyl-AcpB, a FabT co-repressor inStreptococcus pyogenes

Abstract

AbstractMembranes are a universal barrier to all cells. Phospholipids, essential bacterial membrane components, are composed of a polar head and apolar fatty acid (FA) chains. Most bacterial FA are synthesized by the FA synthesis pathway (FASII). In streptococcaceae, enterococci andLactococcus lactis, a unique feedback mechanism controls the FASII gene expression. FabT, encoded in the FASII main locus, is the repressor and it is activated by acyl-ACP. Many Streptococci,Enterococcus faecalis, but notL. lactis, possess two ACPS. AcpA encoding gene is within the FASII locus and is, to a certain extent, coregulated with the FASII genes. Acyl-AcpA is the end product of FASII. AcpB encoding gene is in operon withplsX. The role of AcpB as FabT corepressor is controversial.Streptococcus pyogenes, which causes a wide variety of diseases ranging from mild non-invasive to severe invasive infections, possesses AcpB. In this study, we show by comparing gene repression of FASII genes in wild-type,fabTmutant andacpBmutant strains grown in the presence and the absence of exogenous FAs, that AcpB isS. pyogenesFabT main co-repressor. Also,acpBdeletion impacts the membrane FA composition and adhesion to eucaryotic cells, highlighting the role of AcpB.