1887

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 HgCI 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 HgCI 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.

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/content/journal/micro/10.1099/13500872-142-10-2825
1996-10-01
2019-10-14
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