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The structure of the N-terminal module of the cell wall hydrolase RipA and its role in regulating catalytic activity

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  • Eva Maria Steiner, Karolinska Institutet
  • ,
  • Jeppe Lyngsø
  • ,
  • Jodie E. Guy, Karolinska Institutet
  • ,
  • Gleb Bourenkov, European Molecular Biology Laboratory Hamburg
  • ,
  • Ylva Lindqvist, Karolinska Institutet
  • ,
  • Thomas R. Schneider, European Molecular Biology Laboratory Hamburg
  • ,
  • Jan Skov Pedersen
  • Gunter Schneider, Karolinska Institutet
  • ,
  • Robert Schnell, Karolinska Institutet

RipA plays a vital role during cell division of Mycobacterium tuberculosis by degrading the cell wall peptidoglycan at the septum, allowing daughter cell separation. The peptidoglycan degrading activity relies on the NlpC/P60 domain, and as it is potentially harmful when deregulated, spatial and temporal control is necessary in this process. The N-terminal domain of RipA has been proposed to play an inhibitory role blocking the C-terminal NlpC/P60 domain. Accessibility of the active site cysteine residue is however not limited by the presence of the N-terminal domain, but by the lid-module of the inter-domain linker, which is situated in the peptide binding groove of the crystal structures of the catalytic domain. The 2.2 Å resolution structure of the N-terminal domain, determined by Se-SAD phasing, reveals an all-α-fold with 2 long α-helices, and shows similarity to bacterial periplasmic protein domains with scaffold-building role. Size exclusion chromatography and SAXS experiments are consistent with dimer formation of this domain in solution. The SAXS data from the periplasmic two-domain RipA construct suggest a rigid baton-like structure of the N-terminal module, with the catalytic domain connected by a 24 residue long flexible linker. This flexible linker allows for a catalytic zone, which is part of the spatiotemporal control of peptidoglycan degradation.

Original languageEnglish
JournalProteins: Structure, Function and Bioinformatics
Pages (from-to)912-923
Number of pages12
Publication statusPublished - 11 Oct 2018

    Research areas

  • Cell wall remodeling, NlpC/P60, Peptidoglycan cleavage, Protein structure, SAXS, X-ray crystallography, RipA

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