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  • Title: The LexA-RecA* structure reveals a cryptic lock-and-key mechanism for SOS activation.
    Author: Cory MB, Li A, Hurley CM, Carman PJ, Pumroy RA, Hostetler ZM, Perez RM, Venkatesh Y, Li X, Gupta K, Petersson EJ, Kohli RM.
    Journal: Nat Struct Mol Biol; 2024 Oct; 31(10):1522-1531. PubMed ID: 38755298.
    Abstract:
    The bacterial SOS response plays a key role in adaptation to DNA damage, including genomic stress caused by antibiotics. SOS induction begins when activated RecA*, an oligomeric nucleoprotein filament that forms on single-stranded DNA, binds to and stimulates autoproteolysis of the repressor LexA. Here, we present the structure of the complete Escherichia coli SOS signal complex, constituting full-length LexA bound to RecA*. We uncover an extensive interface unexpectedly including the LexA DNA-binding domain, providing a new molecular rationale for ordered SOS gene induction. We further find that the interface involves three RecA subunits, with a single residue in the central engaged subunit acting as a molecular key, inserting into an allosteric binding pocket to induce LexA cleavage. Given the pro-mutagenic nature of SOS activation, our structural and mechanistic insights provide a foundation for developing new therapeutics to slow the evolution of antibiotic resistance.
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