2f3b

Publication Abstract from PubMed

AMP triggers a 15 degrees subunit-pair rotation in fructose-1,6-bisphosphatase (FBPase) from its active R-state to its inactive T-state. During this transition, a catalytically essential loop (residues 50-72) leaves its active (engaged) conformation. Structures of Ile10-->Asp FBPase and molecular dynamic simulations here reveal factors responsible for loop displacement. AMP/Mg2+ and AMP/Zn2+ complexes of Asp10 FBPase are in intermediate quaternary conformations (completing 12 degrees of subunit-pair rotation), but the complex with Zn2+ provides the first instance of an engaged loop in a near-T quaternary state. The 12 degrees subunit-pair rotation generates close contacts involving the hinges (residues 50-57) and hairpin turns (residues 58-72) of the engaged loops. Additional subunit-pair rotation toward the T-state would make such contacts unfavorable, presumably causing displacement of the loop. Targeted molecular dynamics simulations reveal no steric barriers to subunit-pair rotations up to 14 degrees , followed by the displacement of the loop from the active site. Principal component analysis reveals high-amplitude motions that exacerbate steric clashes of engaged loops in the near-T state. The results of simulations and crystal structures are in agreement: subunit-pair rotations just short of the canonical T-state, coupled with high-amplitude modes, sterically displace the dynamic loop from the active site.

Mechanism of Displacement of a Catalytically Essential Loop from the Active Site of Mammalian Fructose-1,6-bisphosphatase.,Gao Y, Iancu CV, Mukund S, Choe JY, Honzatko RB Biochemistry. 2013 Jul 11. PMID:23844654^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.