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PDBsum entry 1vf7
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Membrane protein
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PDB id
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1vf7
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Contents |
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(+ 5 more)
237 a.a.
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252 a.a.
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the membrane fusion protein, Mexa, Of the multidrug transporter in pseudomonas aeruginosa.
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Authors
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H.Akama,
T.Matsuura,
S.Kashiwagi,
H.Yoneyama,
S.Narita,
T.Tsukihara,
A.Nakagawa,
T.Nakae.
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Ref.
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J Biol Chem, 2004,
279,
25939-25942.
[DOI no: ]
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PubMed id
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Abstract
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The MexAB-OprM efflux pump of Pseudomonas aeruginosa is central to multidrug
resistance of this organism, which infects immunocompromised hospital patients.
The MexA, MexB, and OprM subunits were assumed to function as the membrane
fusion protein, the body of the transporter, and the outer membrane channel
protein, respectively. For better understanding of this important xenobiotic
transporter, we show the x-ray crystallographic structure of MexA at a
resolution of 2.40 A. The global MexA structure showed unforeseen new features
with a spiral assembly of six and seven protomers that were joined together at
one end by a pseudo 2-fold image. The protomer showed a new protein structure
with a tandem arrangement consisting of at least three domains and presumably
one more. The rod domain had a long hairpin of twisted coiled-coil that extended
to one end. The second domain adjacent to the rod alpha-helical domain was
globular and constructed by a cluster of eight short beta-sheets. The third
domain located distal to the alpha-helical rod was globular and composed of
seven short beta-sheets and one short alpha-helix. The 13-mer was shaped like a
woven rattan cylinder with a large internal tubular space and widely opened
flared ends. The 6-mer and 7-mer had a funnel-like structure consisting of a
tubular rod at one side and a widely opened flared funnel top at the other side.
Based on these results, we constructed a model of the MexAB-OprM pump assembly.
The three pairs of MexA dimers interacted with the periplasmic alpha-barrel
domain of OprM via the alpha-helical hairpin, the second domain interacted with
both MexB and OprM at their contact site, and the third and disordered domains
probably interacted with the distal domain of MexB. In this fashion, the MexA
subunit connected MexB and OprM, indicating that MexA is the membrane bridge
protein.
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Figure 2.
FIG. 2. Stereo view of the MexA monomer. Ribbon model of
the MexA monomer: gradient rainbow color of blue to red
indicates N- to C-terminal.
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Figure 3.
FIG. 3. Ribbon diagrams of a representative MexA structure.
A, stereo side view of the structure of the tridecamer. Heptamer
and hexamer are colored red and blue, respectively. B, bottom
view of Fig. 1A (hexamer). Each monomer is distinguished by
alternatively changing the color to blue and gray, respectively.
C, top view of Fig. 1A (heptamer). Each monomer is distinguished
by alternatively changing the color to red and gray,
respectively. The figures were drawn by MolScript version 2.1.2
(40) and Raster 3D version 2.7b (41).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2004,
279,
25939-25942)
copyright 2004.
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