Structure
Volume 30, Issue 11, 3 November 2022, Pages 1479-1493.e9
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Article
Nanobodies targeting LexA autocleavage disclose a novel suppression strategy of SOS-response pathway

https://doi.org/10.1016/j.str.2022.09.004Get rights and content
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Highlights

  • Nanobodies (NbSOSs) binding Escherichia coli LexA with nanomolar affinity have been discovered

  • NbSOSs can inhibit LexA autoproteolysis and block the SOS response axis in bacteria

  • Biophysical characterization of NbSOSs-LexA complexes discloses inhibition mechanism

Summary

Antimicrobial resistance threatens the eradication of infectious diseases and impairs the efficacy of available therapeutics. The bacterial SOS pathway is a conserved response triggered by genotoxic stresses and represents one of the principal mechanisms that lead to resistance. The RecA recombinase acts as a DNA-damage sensor inducing the autoproteolysis of the transcriptional repressor LexA, thereby derepressing SOS genes that mediate DNA repair, survival to chemotherapy, and hypermutation. The inhibition of such pathway represents a promising strategy for delaying the evolution of antimicrobial resistance. We report the identification, via llama immunization and phage display, of nanobodies that bind LexA with sub-micromolar affinity and block autoproteolysis, repressing SOS response in Escherichia coli. Biophysical characterization of nanobody-LexA complexes revealed that they act by trapping LexA in an inactive conformation and interfering with RecA engagement. Our studies pave the way to the development of new-generation antibiotic adjuvants for the treatment of bacterial infections.

Key words

nanobodies
SOS response
antimicrobial resistance
LexA repressor
RecA recombinase
autoproteolysis
inhibition
fluorescence polarization
X-ray crystallography
surface plasmon resonance

Data and code availability

  • The data generated in this study are available upon reasonable request from the lead contact. X-ray structures of LexA-NbSOSs complexes have been deposited at PDB and are publicly available as of the date of publication. Accession numbers are listed in the key resources table.

  • This paper does not report original code.

  • Any additional information required to reanalyze the data reported in this paper is available from the lead contact upon request.

Cited by (0)

9

These authors contributed equally

10

Lead contact