Cleavage of colicin D is necessary for cell killing and requires the inner membrane peptidase LepB |
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Authors: | de Zamaroczy M Mora L Lecuyer A Géli V Buckingham R H |
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Institution: | Institut de Biologie Physico-Chimique, CNRS, UPR 9073, 75005, Paris, France. zamaroczy@ibpc.fr |
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Abstract: | Colicin D is known to kill target cells by cleaving tRNA(Arg). A colicin D-resistant mutant was selected that was altered in the inner membrane leader peptidase, LepB. The substituted residue (Asn274Lys) is located close to the catalytic site. The mutation abolishes colicin D cleavage but not the processing of exported proteins. LepB is required for colicin D cleavage, releasing a small C-terminal fragment that retains full tRNase activity. The immunity protein was found to prevent colicin D processing and furthermore masks tRNase activity, thus protecting colicin D against LepB-mediated cleavage during export. Catalytic colicins share a consensus sequence at their putative processing site. Mutations affecting normal processing of colicin D abolish cytotoxicity without affecting the in vitro tRNase activity. |
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