title: Mutational analysis and chemical modification of Cys24 of lactococcin B, a bacteriocin produced by Lactococcus lactis.
abstract: Using site-directed mutagenesis the single cysteine residue at position 24 of lactococcin B was replaced by all other possible amino acids. Most of these mutant molecules retained bacteriocin activity, with the exception of those in which cysteine was replaced by a positively charged amino acid. This would seem to be in agreement with the authors' earlier observation that treatment of the wild-type molecule with HgCl2 resulted in its inactivation. The factor that causes inactivation of lactococcin B seems to be the introduction of a positive charge at position 24 by HgCl2 rather than oxidation of this residue, as treatment of the bacteriocin with other oxidative chemicals did not interfere with the ability of lactococcin B to dissipate the membrane potential of sensitive cells. Results are also reported which imply that inactive lactococcin B can still bind to its receptor. It can be replaced by an active bacteriocin molecule, resulting in dissipation of the membrane potential.
authors.affiliation: Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Venema
authors.forename: M H
authors.initials: MH
authors.lastname: Dost
authors.forename: G
authors.initials: G
authors.lastname: Venema
authors.forename: J
authors.initials: J
authors.lastname: Kok
mesh_terms: D001430:Bacteriocins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D019327:Copper Sulfate / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry* / Q000494:pharmacology / Q000502:physiology; D004229:Dithiothreitol / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D005561:Formates / Q000494:pharmacology; D013294:Lactococcus lactis / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008626:Mercuribenzoates / Q000494:pharmacology; D008627:Mercuric Chloride / Q000494:pharmacology; D016297:Mutagenesis, Site-Directed; D016877:Oxidants / Q000494:pharmacology; D010084:Oxidation-Reduction; D019163:Reducing Agents / Q000494:pharmacology
chemical_list: C043407:4-mercuribenzoate; D001430:Bacteriocins; D005561:Formates; D008626:Mercuribenzoates; D016877:Oxidants; D019163:Reducing Agents; C008817:peroxyformic acid; C075150:lactococcin B; D008627:Mercuric Chloride; D003545:Cysteine; D019327:Copper Sulfate; D005033:Ethylmaleimide; D004229:Dithiothreitol