The antimicrobial peptides lactoferricin B and magainin 2 cross over the bacterial cytoplasmic membrane and reside in the cytoplasm

The localization of immunolabelled antimicrobial peptides was studied using transmission electron microscopy. Staphylococcus aureus and Escherichia co li were exposed to lactoferricin B (17-41), lactoferricin B (17-31) and D-l actoferricin B (17-31). E. coli was also exposed to cecropin P1 and magaini n 2. The lactoferricins were found in the cytoplasm of both bacteria. In S. aureus the amount of cytoplasmic lactoferricin B (17-41) was time- and con centration-dependent, reaching a maximum within 30 min. Cecropin P1 was con fined to the cell wall. while magainin 2 was found in the cytoplasm of E. c oh. The finding of intracellularly localized magainin is not reported previ ously. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.