We previously reported the crystal structure of the major multidrug exporter AcrB in @entity526 (Murakami, S., Nakashima, R., Yamashita, E., and Yamaguchi, A. (2002) Nature 419, 587-593). The extramembrane headpiece of the AcrB trimer contains a central pore composed of three alpha-helices. Each pore helix belongs to a different monomer. In this study, we constructed @entity462 -scanning mutants as to the residues comprising the pore helix. Of the 21 mutants (D99C to @entity68974 ), 5 (D101C, @entity68975 , @entity68976 , Q112C, and @entity68977 ) showed significantly reduced drug resistance and drug-exporting activity. These residues are localized on one side of the pore helix, i.e. on the wall of the pore. These observations strongly indicate the important role of this pore in the drug transport process. A @entity8816 binding experiment revealed that the pore is in the closed state, and the thickness of the permeability barrier in the middle of the pore corresponds to 2.5 alpha-helical turns. Two mutants ( @entity68975 and Q112C), which showed the greatest loss of activity of all of the pore mutants, were detected in the form of @entity1520 cross-linking dimers under normal conditions, suggesting that a conformational change of the pore is indispensable during the transport process.

Extramembrane central pore of multidrug exporter AcrB in XXXX plays an important role in drug transport.

@entity68976 :: ('p|SUB|N|109|C', 'ProteinMutation') :: ['N109C'] @entity68974 :: ('p|SUB|P|119|C', 'ProteinMutation') :: ['P119C'] @entity462 :: ('MESH:D003545', 'Chemical') :: ['cysteine'] @entity68975 :: ('p|SUB|V|105|C', 'ProteinMutation') :: ['V105C'] @entity8816 :: ('MESH:D005033', 'Chemical') :: ['N-ethylmaleimide'] @entity68977 :: ('p|SUB|P|116|C', 'ProteinMutation') :: ['P116C'] @entity1520 :: ('CHEBI:48343', 'Chemical') :: ['disulfide'] @entity526 :: ('562', 'Species') :: ['Escherichia coli']
@entity526 :: (562,Species) :: ['Escherichia coli']
