The Stable Interaction Between Signal Peptidase LepB of Escherichia coli and Nuclease Bacteriocins Promotes Toxin Entry into the Cytoplasm.
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 colicin D for 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 nanomolar Kd 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.
From the Institut de Biologie Physico-Chimique, CNRS, FRE 3630 (UPR 9073), 75005 Paris, France.
Liliana
L
Mora
Institut de Biologie Physico-Chimique, CNRS, UMR 7099 (Université Paris 7-Diderot), 75005 Paris, France.
Karine
K
Moncoq
Institut Pasteur, PFBMI, CNRS, UMR 3528, 75015 Paris, France, and.
Patrick
P
England
Institute of Integrative Cellular Biology, CEA, CNRS (Université Paris 11), 91405 Orsay, France.
Jacques
J
Oberto
From the Institut de Biologie Physico-Chimique, CNRS, FRE 3630 (UPR 9073), 75005 Paris, France, zamaroczy@ibpc.fr.
Miklos
M
de Zamaroczy
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D001430:Bacteriocins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D003593:Cytoplasm / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003851:Deoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012260:Ribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D001427:Bacterial Toxins; D001430:Bacteriocins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C501879:colicin D immunity protein, E coli; D003851:Deoxyribonucleases; D012260:Ribonucleases; D012697:Serine Endopeptidases; C026515:type I signal peptidase
LepB; bacteriocin; colicin; endonuclease; membrane; microbiology; protease; protein import; toxicity