lantibiotic immunity ABC transporter MutE/EpiE family permease (also called ABC-2 transporter MutE/EpiE family permease) subunit
This subfamily includes lantibiotic ABC transporter permease subunits EpiE, MutE, SlvE and NisE, which are highly hydrophobic, integral membrane proteins, and part of the bacitracin ABC transport system that confers resistance to the Gram-positive bacteria in which this system operates, specifically to the lantibiotics mutacin, epidermin, nisin and salivaricin, respectively. Lantibiotics are small peptides, produced by Gram-positive bacteria, which are ribosomally-synthesized as pre-peptides and act by disrupting membrane integrity. Genes encoding the lantibiotic ABC transporter subunits are highly organized in operons containing all the genes required for maturation, transport, immunity, and synthesis. For example, in Staphylococcus epidermidis Tu3298, the lantibiotic epidermin is active against other Gram-positive bacteria via various modes of actions; however, its self-protection against the pore-forming epidermin is mediated by the ABC transporter immunity proteins composed of EpiF, EpiE and EpiG; the EpiE permease subunit transports epidermin to the surface and expels it from the membrane. This subfamily also includes the lantibiotic ABC transporter permease subunits MutE, SlvF, and NisE. Self-protection of the mutacin-producing strain Streptococcus mutans CH43 against the pore-forming lantibiotic mutacin is mediated by an ABC transporter composed of MutF, MutE and MutG. In salivaricin D-producing strain Streptococcus salivarius 5M6c, self-immunity against the intrinsically trypsin-resistant salivaricin is mediated via ABC transporter proteins SlvF, SlvE and SlvG, while in Lactococcus lactis, self-immunity against nisin is mediated by the ABC transporter NisFEG. The MutE, NisE and SlvF permease subunits transport mutacin, nisin and salivaricin, respectively to the surface and expel them from the membrane.