Description |
The structure of the neutral form of fructose-1,6-bisphosphatase complexed with AMP (and MG) was determined and shown to have a different quaternary structure than that of the unliganded enzyme. Specifically, two major quaternary conformational changes are observed: (1) A twist of dimer C3-C4 about the molecular 2-fold axis p by roughly 19 degrees relataive to dimer C1-C2, and (2) a translation of approximately 1 A of the AMP domains. The conformational shift between the T and R allosteric forms induced by AMP binding is also observed to induce a large movment of residues in the AMP domain.Superimposition of the two structures show average C-alpha displacements over the entire FBP domain in these complexes of 0.35 A. Glu97, Glu97, and Asp121 shift over 1 A, while C-alpha positions for Asp118 and Glu280 are observed to move 0.5 and 0.3 A, respectively. The largest changes in the R to T transition occur in the interdimeric interface, mainly made up of helices H1, H2, and H3. The dimer C3-C4 undergoes a 19 degree twist, placing the upper H2 helix close to the lower H3 helix in the T form. |
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