The invo
lvement of transporters in mu
ltidrug resistance of bacteria is an increasing
ly cha
llengingprob
lem, and most of the pumps identified so far use the protonmotive gradient as the energy source. Anew member of the ATP-binding cassette (ABC) fami
ly, known in
Bacillus subtilis as YvcC andhomo
logous to each ha
lf of mamma
lian P-g
lycoprotein and to LmrA of
Lactococcus lactis, has beenstudied here. The
yvcC gene was constitutive
ly expressed in
B. subtilis throughout its growth, and aknockout mutant showed a
lower rate of ethidium eff
lux than the wi
ld-type strain. Overexpression of
yvcC in
Escherichia coli a
llowed the preparation of high
ly enriched inverted-membrane vesic
les thatexhibited high transport activities of three f
luorescent drugs, name
ly, Hoechst 33342, doxorubicin, and7-aminoactinomycin D. After so
lubi
lization with
n-dodecy
l le">-
D-ma
ltoside, the hexahistidine-tagged YvcCwas purified by a one-step affinity chromatography, and its abi
lity to bind many P-g
lycoprotein effectorswas evidenced by f
luorescence spectroscopy experiments. Co
llective
ly, these resu
lts showed that YvcCis a mu
ltidrug ABC transporter functiona
lly active in wi
ld-type
B. subtilis, and YvcC was therefore renamedBmrA for
Bacillus mu
ltidrug
resistance
ATP. Besides, reconstitution of YvcC into
liposomes
led to thehighest, vanadate-sensitive, ATPase activity reported so far for an ABC transporter. Interesting
ly, such ahigh ATP hydro
lysis proceeds with a positive cooperativity mechanism, a property on
ly found so farwith ABC importers.