Modulation of enrofloxacin binding in OmpF by Mg as revealed by the analysis of fast flickering single-porin current

Antibiotics have to penetrate the outer membrane to enter Gram-negative bacteria. One possible pathway is the diffusion through the lipid phase (Ribeiro et al., 2011), especially for the hydrophobic first-generation quinolones (Delcour, 2009). However, the outer membrane also contains a plethora of channel-forming pro teins called porins. Recent studies on multidrug resistance revealed modified porin patterns in the outer membrane. Resistant cells were found to reduce the number, to show mutated porins, or to express different porins (Pagès et al., 2008). These findings suggested that a reduced permeation through porins is one possible contribution to drug resistance and motivated studies on interactions between antibiotics and porins (James et al., 2009; Tran et al., 2010). Here, the major outer membrane protein F (OmpF) isolated from Escherichia coli is in the focus (Nikaido, 2003) because it is suggested that newer, more hydrophilic