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Mol Microbiol. 2000 Jul;37(1):67-80.

Temperature-regulated efflux pump/potassium antiporter system mediates resistance to cationic antimicrobial peptides in Yersinia.

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Department of Medical Biochemistry, Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku, Finland.


Most bacterial pathogens are resistant to cationic antimicrobial peptides (CAMPs) that are key components of the innate immunity of both vertebrates and invertebrates. In Gram-negative bacteria, the known CAMPs resistance mechanisms involve outer membrane (OM) modifications and specifically those in the lipopolysaccharide (LPS) molecule. Here we report, the characterization of a novel CAMPs resistance mechanism present in Yersinia that is dependent on an efflux pump/potassium antiporter system formed by the RosA and RosB proteins. The RosA/RosB system is activated by a temperature shift to 37 degrees C, but is also induced by the presence of the CAMPs, such as polymyxin B. This is the first report of a CAMPs resistance system that is induced by the presence of CAMPs. It is proposed that the RosA/RosB system protects the bacteria by both acidifying the cytoplasm to prevent the CAMPs action and pumping the CAMPs out of the cell.

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