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PDBsum entry 3e2d
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References listed in PDB file
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Key reference
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Title
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The 1.4 a crystal structure of the large and cold-Active vibrio sp. Alkaline phosphatase.
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Authors
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R.Helland,
R.L.Larsen,
B.Asgeirsson.
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Ref.
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Biochim Biophys Acta, 2009,
1794,
297-308.
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PubMed id
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Abstract
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Alkaline phosphatase (AP) from the cold-adapted Vibrio strain G15-21 is among
the AP variants with the highest known k(cat) value. Here the structure of the
enzyme at 1.4 A resolution is reported and compared to APs from E. coli, human
placenta, shrimp and the Antarctic bacterium strain TAB5. The Vibrio AP is a
dimer although its monomers are without the long N-terminal helix that embraces
the other subunit in many other APs. The long insertion loop, previously noted
as a special feature of the Vibrio AP, serves a similar function. The surface
does not have the high negative charge density as observed in shrimp AP, but a
positively charged patch is observed around the active site that may be
favourable for substrate binding. The dimer interface has a similar number of
non-covalent interactions as other APs and the "crown"-domain is the
largest observed in known APs. Part of it slopes over the catalytic site
suggesting that the substrates may be small molecules. The catalytic serines are
refined with multiple conformations in both monomers. One of the ligands to the
catalytic zinc ion in binding site M1 is directly connected to the crown-domain
and is closest to the dimer interface. Subtle movements in metal ligands may
help in the release of the product and/or facilitate prior dephosphorylation of
the covalent intermediate. Intersubunit interactions may be a major factor for
promoting active site geometries that lead to the high catalytic activity of
Vibrio AP at low temperatures.
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