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Mutational analysis and chemical modification of Cys24 of lactococcin B, a bacteriocin produced by Lactococcus lactis

Koen Venema

Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands

¹Author for correspondence: Gerard Venema. Tel: +31 50 3632092. Fax: +31 50 3632348.

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 HgCI₂ 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 HgCI₂ 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.

Present address: Department of Food Science, North Carolina State University, Box 7624, Raleigh, NC 27695, USA.

This article has been cited by other articles:

				L. M. Cintas, M. P. Casaus, C. Herranz, I. F. Nes, and P. E. Hernandez Review: Bacteriocins of Lactic Acid Bacteria Food Science and Technology International, August 1, 2001; 7(4): 281 - 305. [Abstract] [PDF]