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Title
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Structure of native porcine pancreatic elastase at 1.65 A resolutions.
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Authors
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E.Meyer,
G.Cole,
R.Radhakrishnan,
O.Epp.
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Ref.
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Acta Crystallogr B, 1988,
44,
26-38.
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PubMed id
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Abstract
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The structure of native porcine pancreatic elastase in 70% methanol has been
refined using film data to 1.65 A resolution, R = 0.169. A total of 134
molecules of water (but no methanol) has been refined. This structure, because
of its native state and modestly high resolution, serves as the basis for
comparison with other elastase structures complexed with natural or synthetic
ligands. Internal structured water occupies distinct regions. Two regions (IW1
and IW7) suggest a mechanism for equalizing 'hydrostatic pressure' related to
ligand binding and release. A third region (IW4) forms part of a
hydrogen-bonding network linking the catalytic Ser 195 O gamma with a remote
(13.4 A) surface of the enzyme. A comparison with the structures of all known
serine proteases reveals that a linkage of Ser O gamma to remote surface is
conserved in all cases, suggesting that the accepted catalytic mechanism of
serine proteases needs to be re-evaluated. One possible mechanism for base
catalysis of Ser O gamma H proton extraction is presented.
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