1CNQ: Fructose-1,6-Bisphosphatase Complexed With Fructose-6-Phosphate And Zinc Ions

A disordered loop (loop 52-72, residues 52-72) in crystal structures of fructose-1,6-bisphosphatase (FBPase) has been implicated in regulatory and catalytic phenomena by studies in directed mutation. A crystal structure of FBPase in a complex with three zinc cations and the products fructose 6-phosphate (F6P) and phosphate (Pi) reveals loop 52-72 for the first time in a well-defined conformation with strong electron density. Loop 52-57 interacts primarily with the active site of its own subunit. Asp68 of the loop hydrogen bonds with Arg276 and a zinc cation located at the putative potassium activation site. Leu56 and Tyr57 of the loop pack against hydrophobic residues from two separate subunits of FBPase. A mechanism of allosteric regulation of catalysis is presented, in which AMP, by binding to its allosteric pocket, displaces loop 52-72 from the active site. Furthermore, the current structure suggests that both the alpha- and beta-anomers of F6P can be substrates in the reverse reaction catalyzed by FBPase. Mechanisms of catalysis are proposed for the reverse reaction in which Asp121 serves as a catalytic base for the alpha-anomer and Glu280 serves as a catalytic base for the beta-anomer.
PDB ID: 1CNQDownload
MMDB ID: 10261
PDB Deposition Date: 1999/5/21
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.27  Å
Source Organism:
Similar Structures:
Biological Unit for 1CNQ: tetrameric; determined by author and by software (PISA,PQS)
Molecular Components in 1CNQ
Label Count Molecule
Proteins (4 molecules)
Fructose-1,6-bisphosphatase(Gene symbol: FBP1)
Molecule annotation
Chemicals (24 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB