Toxic protein AapA1

UniProtKB accession:  P0DUM4

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UniProtKB description:  May be involved in response to oxidative stress (Probable). Toxic component of a type I toxin-antitoxin (TA) system. When overexpression is induced in situ in the absence of its cognate antisense RNA antitoxin IsoA1 it leads to cell growth arrest and cell death without lysis. Neutralized by IsoA1 RNA which forms an extensive duplex with the mRNA (PubMed:28077560, PubMed:33229580, PubMed:31476357). Binds artificial prokaryotic and eukaryotic lipid membranes, with 30-fold higher affinity for prokaryotic membranes. Molecular dynamics suggests the peptide penetrates the membrane leading to lipid reorganization and thinning of the bilayer (PubMed:31476357). Induction of toxin in the absence of antitoxin RNA causes a fast conversion of cells from spiral-shaped to coccoid forms; cells have no visible membrane defects and resemble wild-type 'aging coccoids'. Toxin causes a moderate decrease in membrane potential and ATP content and alterations in peptidoglycan muropeptide abundance; GlcNAc-MurNAc dipeptides increase while GlcNAc-MurNAc tripeptides decrease (i.e. a faster phenocopy of cell aging). Deletion of all 6 AapA/IsoA TA loci in strain B128 leads to slower than wild-type conversion of H2O2-treated cells to the coccoid form. This suggests oxidative stress triggers coccoid transformation via these type I TA systems, although other factors eventually drive the morphology change (PubMed:33229580).