Venema K, Dost M H, Venema G, Kok J
Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
Microbiology (Reading). 1996 Oct;142 ( Pt 10):2825-30. doi: 10.1099/13500872-142-10-2825.
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.
利用定点诱变技术，将乳酸乳球菌素B第24位的单个半胱氨酸残基替换为所有其他可能的氨基酸。除了那些半胱氨酸被带正电荷的氨基酸取代的突变分子外，大多数这些突变分子都保留了细菌素活性。这似乎与作者早期的观察结果一致，即野生型分子用HgCl2处理会导致其失活。导致乳酸乳球菌素B失活的因素似乎是HgCl2在第24位引入了正电荷，而不是该残基的氧化，因为用其他氧化化学物质处理细菌素不会干扰乳酸乳球菌素B消散敏感细胞膜电位的能力。还报告了一些结果，这些结果表明无活性的乳酸乳球菌素B仍然可以与其受体结合。它可以被一个活性细菌素分子取代，从而导致膜电位的消散。
