1EYK: Fructose-1,6-bisphosphatase Complex With Amp, Zinc, Fructose-6- Phosphate And Phosphate (t-state)

Crystal structures of metal-product complexes of fructose 1, 6-bisphosphatase (FBPase) reveal competition between AMP and divalent cations. In the presence of AMP, the Zn(2+)-product and Mg(2+)-product complexes have a divalent cation present only at one of three metal binding sites (site 1). The enzyme is in the T-state conformation with a disordered loop of residues 52-72 (loop 52-72). In the absence of AMP, the enzyme crystallizes in the R-state conformation, with loop 52-72 associated with the active site. In structures without AMP, three metal-binding sites are occupied by Zn(2+) and two of three metal sites (sites 1 and 2) by Mg(2+). Evidently, the association of AMP with FBPase disorders loop 52-72, the consequence of which is the release of cations from two of three metal binding sites. In the Mg(2+) complexes (but not the Zn(2+) complexes), the 1-OH group of fructose 6-phosphate (F6P) coordinates to the metal at site 1 and is oriented for a nucleophilic attack on the bound phosphate molecule. A mechanism is presented for the forward reaction, in which Asp74 and Glu98 together generate a hydroxide anion coordinated to the Mg(2+) at site 2, which then displaces F6P. Development of negative charge on the 1-oxygen of F6P is stabilized by its coordination to the Mg(2+) at site 1.
PDB ID: 1EYKDownload
MMDB ID: 14198
PDB Deposition Date: 2000/5/7
Updated in MMDB: 2017/10
Experimental Method:
x-ray diffraction
Resolution: 2.23  Å
Source Organism:
Similar Structures:
Biological Unit for 1EYK: tetrameric; determined by author and by software (PISA,PQS)
Molecular Components in 1EYK
Label Count Molecule
Proteins (4 molecules)
Fructose-1,6-bisphosphatase(Gene symbol: FBP1)
Molecule annotation
Chemicals (16 molecules)
* Click molecule labels to explore molecular sequence information.

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