Phosphofructokinase (PFK): Difference between revisions

Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Judy Voet, Eran Hodis, Zach Westrick, David Canner, Michal Harel, Alexander Berchansky, Jaime Prilusky, Joel L. Sussman, Ann Taylor

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 KINEMAGE 2 comes up in view 1: The Allosteric Site, in the R state showing the phosphate group of F6P (hotpink) bound in the enzyme's active site in a hydrogen bonded salt bridge (dashed white lines) with the side chain of Arg 162 (cyan). An ADP (yellow; "ADP-allo") occupies the adjacent allosteric site. Click once on "ANIMATE" to switch to the T state. This replaces the ADP in the R state allosteric site with the inhibitor and PEP analog PGC (gold). F6P no longer occupies the active site but its position in the R state is indicated by the "ghost" F6P (gray; viewed by clicking on "F6P site").
-	What happens to the central polypeptide helical segment (residues 149-164) in the R to T transition? <scene name='37/376373/161_162_r/1'>R helix, 161 and 162</scene>  <scene name='37/376373/161_162_t/1'>T helix, 161 and 162</scene> What does this do to the relative positions of the negatively charged Glu 161 and the positively charged Arg 162? What influence would the absence of the positive charge of Arg 162 have on the binding of F6P? Does this explain, at least in part, why T state PFK has low affinity for F6P? Go to View 2: Closeup, for a closeup of the F6P-sidechain interactions. Center the molecules by choosing "pickcenter" from the "tools" menu and clicking on athe atom you'd like to be in the center. Slide the "zoom" slider to enlarge the view.
+	What happens to the central polypeptide helical segment (residues 149-164) in the R to T transition? <scene name='37/376373/161_162_r/1'>R helix, 161 and 162</scene>  <scene name='37/376373/161_162_t/2'>T helix, 161 and 162</scene> What does this do to the relative positions of the negatively charged Glu 161 and the positively charged Arg 162? What influence would the absence of the positive charge of Arg 162 have on the binding of F6P? Does this explain, at least in part, why T state PFK has low affinity for F6P? Go to View 2: Closeup, for a closeup of the F6P-sidechain interactions. Center the molecules by choosing "pickcenter" from the "tools" menu and clicking on athe atom you'd like to be in the center. Slide the "zoom" slider to enlarge the view.
 ==Site-Directed Mutagenesis==
 At one time, the negative charge of Glu 161 was thought to have a negative effect on F6P binding in the T state. This idea has not been supported by site-directed mutagenesis experiments<ref>PMID:10759544</ref>.  Several mutant PFKs have been made, including R162A, E161A and R162A/E161A. The R162A mutation caused a 30-fold decrease in F6P binding. The E161A mutation, however, had little effect on the ability of PEP to inhibit F6P binding.