The Stable Interaction Between Signal Peptidase LepB of Escherichia coli and Nuclease Bacteriocins Promotes Toxin Entry into the Cytoplasm.
- Resource Type
- Article
- Authors
- Mora, Liliana; Moncoq, Karine; England, Patrick; Oberto, Jacques; de Zamaroczy, Miklos
- Source
- Journal of Biological Chemistry. 12/25/2015, Vol. 290 Issue 52, p30783-30796. 14p.
- Subject
- *ESCHERICHIA coli proteins
*BACTERIOCINS
*CYTOPLASM
*PEPTIDASE
*NUCLEASES
*TOXINS
*OPEN reading frames (Genetics)
*TRANSFER RNA
*PHYSIOLOGY
- Language
- ISSN
- 0021-9258
LepB is a key membrane component of the cellular secretion machinery, which releases secreted proteins into the periplasm by cleaving the inner membrane-bound leader. We showed that LepB is also an essential component of the machinery hijacked by the tRNase colicinDfor its import. Here we demonstrate that this non-catalytic activity of LepB is to promote the association of the central domain of colicin D with the inner membrane before the FtsH-dependent proteolytic processing and translocation of the toxic tRNase domain into the cytoplasm. The novel structural role of LepB results in a stable interaction with colicin D, with a stoichiometry of 1:1 and a nanomolarKd determined in vitro. LepB provides a chaperone-like function for the penetration of several nuclease-type bacteriocins into target cells. The colicin-LepB interaction is shown to require only a short peptide sequence within the central domain of these bacteriocins and to involve residues present in the short C-terminal Box E of LepB. Genomic screening identified the conserved LepB binding motif in colicin-like ORFs from 13 additional bacterial species. These findings establish a new paradigm for the functional adaptability of an essential inner-membrane enzyme. [ABSTRACT FROM AUTHOR]