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PDBsum entry 2eip
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Inorganic pyrophosphatase
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PDB id
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2eip
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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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Structure of escherichia coli inorganic pyrophosphatase at 2.2 a resolution.
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Authors
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J.Kankare,
T.Salminen,
R.Lahti,
B.S.Cooperman,
A.A.Baykov,
A.Goldman.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1996,
52,
551-563.
[DOI no: ]
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PubMed id
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Abstract
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The refined crystal structures of hexameric soluble inorganic pyrophosphatase
from E. coli (E-PPase) are reported to R factors of 18.7 and 18.3% at 2.15 and
2.2 A, respectively. The first contains one independent monomer; the other, two
independent monomers, in an R32 unit cell. Because the E-PPase monomer is small
with a large open active site, there are relatively few hydrophobic interactions
that connect the active-site loops to the five-stranded twisted beta-barrel that
is the hydrophobic core of the molecule. The active-site loops are, however,
held in place by interactions between monomers around the threefold and twofold
symmetry axes of the D(3) hexamer. Consequently, mutations of active-site
residues (such as Glu20 and Lysl04) often affect protein stability and
oligomeric structure. Conversely, mutations of residues in the interface between
monomers (such as His136 and Hisl40) not only affect oligomeric structure but
also affect active-site function. The effects of the H136Q and H140Q variants
can be explained by the extended ionic interaction between H140, D143 and H136'
of the neighbouring monomer. This interaction is further buttressed by an
extensive hydrogen-bonding network that appears to explain why the E-PPase
hexamer is so stable and also why the H136Q and H140Q variant proteins are less
stable as hexamers.
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Figure 4.
Fig. 4. (a). A stereo diagram
of the C~
trace of
E. coli
PPase showing the
overall topology of the enzyme.
The colouring scheme follows this
definition: the barrel and the parts
belonging to it are coloured green
and the excursions red. The resi-
dues belonging
to the hydrophobic
core of the barrel are blue and the
residues which participate in inter-
monomeric contacts are yellow.
The missing loops in the short
c-axis form and the long c-axis
form monomer II are shown as
dotted lines. This figure was drawn
using
MOLSCRIPT
(Kraulis,
1991).
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Figure 7.
Fig. 7. (a) Hydrophilic intratrimefic
contacts between monomers
related by the threefold axis
sh6wn in a
MOLSCRIPT
(Kraulis,
1991) stereo diagram. Two adja-
cent symmetry mates around the
threefold axis are dark and light
grey and hydrogen bonds are
shown with dashed lines. The
curved arrows pointing upwards
is f12, the one pointing down is 133.
(b) Hydrophobic intratrimeric con-
tacts between monomers related by
the threefold axis shown in a
MOLSCRIPT
(Kraulis, 1991
)
stereo diagram. Two adjacent sym-
metry mates around the threefold
axis are dark and light grey. The
'residues involved in hydrophobic
interactions are marked. The view
is approximately
the same as in (a),
but 'lower down' on the long fl2-
/33 loop; in (a), the top of the loop
can be seen.
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(1996,
52,
551-563)
copyright 1996.
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Secondary reference #1
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Title
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New crystal forms of escherichia coli and saccharomyces cerevisiae soluble inorganic pyrophosphatases.
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Authors
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P.Heikinheimo,
T.Salminen,
R.Lahti,
B.Cooperman,
A.Goldman.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1995,
51,
399-401.
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PubMed id
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Secondary reference #2
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Title
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The structure of e.Coli soluble inorganic pyrophosphatase at 2.7 a resolution.
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Authors
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J.Kankare,
G.S.Neal,
T.Salminen,
T.Glumoff,
T.].Glumhoff t [corrected to glumoff,
B.S.Cooperman,
R.Lahti,
A.Goldman.
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Ref.
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Protein Eng, 1994,
7,
823-830.
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PubMed id
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