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Title
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Conformational transition of fructose-1,6-bisphosphatase: structure comparison between the AMP complex (T form) and the fructose 6-phosphate complex (R form).
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Authors
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H.M.Ke,
J.Y.Liang,
Y.P.Zhang,
W.N.Lipscomb.
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Ref.
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Biochemistry, 1991,
30,
4412-4420.
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PubMed id
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Abstract
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A structure of the neutral form of fructose-1,6-bisphosphatase complexed with
AMP has been determined by the molecular replacement method and refined at a
2.5-A resolution to a crystallographic R factor of 0.169. The root-mean-square
errors of the structure from standard geometry are 0.013 A for bond lengths and
2.99 degrees for bond angles. Comparison of the AMP complex with the F6P complex
shows that dimer C3-C4 twists about 19 degrees about a molecular 2-fold axis
when dimers C1-C2 of the R and T forms of the enzyme are superimposed one
another and that a slight shift of about 1 A of the AMP domain partially
compensates this twist. The R to T transition of the enzyme does not
significantly change the conformation of the F6P-binding site. However, residues
at the divalent metal site and the AMP site show significant positional shifts.
If these results can be extended to substrate in place of F6P, they suggest that
regulation of the enzyme by AMP may occur partly through effects on metal-ion
affinity or position. AMP binds to the same sites of the T and R forms, but only
half-occupancy was observed in the alkaline R form. Sequential binding of AMP,
at least in pairs, is suggested as the unligated R form is converted to the T
form. Two possible pathways are suggested for allosteric communication over
about 28 A between the AMP site and the active site: one via helices H1, H2, and
H3 and another via the eight-stranded beta-sheet.(ABSTRACT TRUNCATED AT 250
WORDS)
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