K. Sakamoto et al., Hop resistance in the beer spoilage bacterium Lactobacillus brevis is mediated by the ATP-binding cassette multidrug transporter HorA, J BACT, 183(18), 2001, pp. 5371-5375
Lactobacillus brevis is a major contaminant of spoiled beer. The organism c
an grow in beer in spite of the presence of antibacterial hop compounds tha
t give the beer a bitter taste. The hop resistance in L. brevis is, at leas
t in part, dependent on the expression of the horA gene. The deduced amino
acid sequence of HorA is 53% identical to that of LmrA, an ATP-binding cass
ette multidrug transporter in Lactococcus lactis. To study the role of HorA
in hop resistance, HorA was functionally expressed in L. lactis as a hexa-
histidine-tagged protein using the nisin-controlled gene expression system.
HorA expression increased the resistance of L. lactis to hop compounds and
cytotoxic drugs. Drug transport studies with L. lactis cells and membrane
vesicles and with proteoliposomes containing purified HorA protein identifi
ed HorA as a new member of the ABC family of multidrug transporters.