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PDBsum entry 1vkr
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Contents |
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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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Three-Dimensional solution structure of the cytoplasmic b domain of the mannitol transporter iimannitol of the escherichia coli phosphotransferase system.
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Authors
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P.M.Legler,
M.Cai,
A.Peterkofsky,
G.M.Clore.
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Ref.
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J Biol Chem, 2004,
279,
39115-39121.
[DOI no: ]
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PubMed id
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Abstract
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The solution structure of the cytoplasmic B domain of the mannitol (Mtl)
transporter (II(Mtl)) from the mannitol branch of the Escherichia coli
phosphotransferase system has been solved by multidimensional NMR spectroscopy
with extensive use of residual dipolar couplings. The ordered IIB(Mtl) domain
(residues 375-471 of II(Mtl)) consists of a four-stranded parallel beta-sheet
flanked by two helices (alpha(1) and alpha(3)) on one face and helix alpha(2) on
the opposite face with a characteristic Rossmann fold comprising two
right-handed beta(1)alpha(1)beta(2) and beta(3)alpha(2)beta(4) motifs. The
active site loop is structurally very similar to that of the eukaryotic protein
tyrosine phosphatases, with the active site cysteine (Cys-384) primed in the
thiolate state (pK(a) < 5.6) for nucleophilic attack at the phosphorylated
histidine (His-554) of the IIA(Mtl) domain through stabilization by hydrogen
bonding interactions with neighboring backbone amide groups at positions i +
2/3/4 from Cys-384 and with the hydroxyl group of Ser-391 at position i + 7.
Modeling of the phosphorylated state of IIB(Mtl) suggests that the phosphoryl
group can be readily stabilized by hydrogen bonding interactions with backbone
amides in the i + 2/4/5/6/7 positions as well as with the hydroxyl group of
Ser390 at position i + 6. Despite the absence of any significant sequence
identity, the structure of IIB(Mtl) is remarkably similar to the structures of
bovine protein tyrosine phosphatase (which contains two long insertions relative
to IIB(Mtl)) and the cytoplasmic B component of enzyme II(Chb), which fulfills
an analogous role to IIB(Mtl) in the N,N'-diacetylchitobiose branch of the
phosphotransferase system. All three proteins utilize a cysteine residue in the
nucleophilic attack of a phosphoryl group covalently bound to another protein.
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Figure 2.
FIG. 2. Comparison of the polypeptide folds of IIB^Mtl,
BPTP, and IIB^Chb. Ribbon diagrams showing two approximately
orthogonal views of IIB^Mtl (red)(A), BPTP (B), and IIB^Chb (C).
In panels B and C the regions of the polypeptide of BPTP and
IIB^Chb, respectively, that superimpose on IIB^Mtl are shown in
blue with the remainder in gray. Also shown in each case is the
location of the active site cysteine. Single-letter amino acid
abbreviations are used. For IIB^Mtl and BPTP (PDB accession code
1DG9 [PDB]
) (64), the C[  ]atoms of 81 residues
(sequence identity 12.3%) superimpose with an r.m.s. difference
of 1.9 Å; for IIB^Mtl and IIB^Chb (PDB accession code 1H9C
[PDB]
) (19), the C[ ]atoms of 74 residues
(sequence identity 8.1%) superimpose with an r.m.s. difference
of 2.0 Å. (The structural alignments are as follows:
residues 378-411, 411-417, 422-429, 429-444, 444-450, and
455-466 of IIB^Mtl superimpose on residues 6-39, 40-46, 83-90,
91-103, 111-117, and 146-157, respectively of BPTP; residues
378-385, 386-408, 409-420, 421-430, and 431-451 of IIB^Mtl
superimpose on residues 4-11, 11-33, 33-44, 48-57, and 61-81,
respectively of IIB^Chb).
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Figure 3.
FIG. 3. The active site of IIB^Mtl. A, stereo view of the
active site with the backbone in light blue, side chains in red,
Cys-384 in orange, and the backbone NH bonds in dark blue with
the H[N] protons represented by small spheres. B, possible
mechanism of phosphoryl transfer from IIA^Mtl to IIB^Mtl.
Single-letter amino acid abbreviations are used with position
numbers.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2004,
279,
39115-39121)
copyright 2004.
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