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PDBsum entry 4p3m
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References listed in PDB file
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Key reference
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Title
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Conformational transitions driven by pyridoxal-5'-Phosphate uptake in the psychrophilic serine hydroxymethyltransferase from psychromonas ingrahamii.
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Authors
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S.Angelaccio,
F.Dworkowski,
A.Di bello,
T.Milano,
G.Capitani,
S.Pascarella.
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Ref.
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Proteins, 2014,
82,
2831-2841.
[DOI no: ]
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PubMed id
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Abstract
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Serine hydroxymethyltransferase (SHMT) is a pyridoxal-5'-phosphate
(PLP)-dependent enzyme belonging to the fold type I superfamily, which catalyzes
in vivo the reversible conversion of l-serine and tetrahydropteroylglutamate (H4
PteGlu) to glycine and 5,10-methylenetetrahydropteroylglutamate (5,10-CH2 -H4
PteGlu). The SHMT from the psychrophilic bacterium Psychromonas ingrahamii
(piSHMT) had been recently purified and characterized. This enzyme was shown to
display catalytic and stability properties typical of psychrophilic enzymes,
namely high catalytic activity at low temperature and thermolability. To gain
deeper insights into the structure-function relationship of piSHMT, the
three-dimensional structure of its apo form was determined by X-ray
crystallography. Homology modeling techniques were applied to build a model of
the piSHMT holo form. Comparison of the two forms unraveled the conformation
modifications that take place when the apo enzyme binds its cofactor. Our
results show that the apo form is in an "open" conformation and
possesses four (or five, in chain A) disordered loops whose electron density is
not visible by X-ray crystallography. These loops contain residues that interact
with the PLP cofactor and three of them are localized in the major domain that,
along with the small domain, constitutes the single subunit of the SHMT
homodimer. Cofactor binding triggers a rearrangement of the small domain that
moves toward the large domain and screens the PLP binding site at the solvent
side. Comparison to the mesophilic apo SHMT from Salmonella typhimurium suggests
that the backbone conformational changes are wider in psychrophilic SHMT.
Proteins 2014; 82:2831-2841. © 2014 Wiley Periodicals, Inc.
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