Download MendeleyRole of a dynamic loop in cation activation and allosteric regulation of recombinant porcine fructose-1,6-bisphosphatase.
Choe, J.Y., Poland, B.W., Fromm, H.J., Honzatko, R.B.(1998) Biochemistry 37: 11441-11450
- PubMed: 9708979
- DOI: https://doi.org/10.1021/bi981112u
- Primary Citation of Related Structures:
1CNQ - PubMed Abstract:
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.
Organizational Affiliation:
Department of Biochemistry and Biophysics, Iowa State University, Ames 50011, USA.
