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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 	This Kinemage exercise consists of two kinemage scenes that illustrate some of the allosterically-induced conformational changes that occur in PFK from Bacillus stearothermophilus.
+{{Clear}}
 == Conformational Changes in a Dimeric Unit of PFK==
 	 This kinemage shows the two subunits of the tetramer whose interface contains two active sites.
 <kinemage align="right" width="450" height= "450" file="PFK1.kin" />
-The first view, 1: PFK dimer, shows the two subunits in their R state conformation as represented by their Ca backbones with Subunit 1 in pinktint and Subunit 2 in pink. Two side chains in each subunit are shown, those of Glu 161 (red) and Arg 162 (cyan), which are part of the F6P binding site in the  T and R states, srespectively(see below). An F6P (hotpink) and an ADP (green; "ADP-active") are bound in the active site of each subunit. An additional ADP (yellow; "ADP-allo") is bound in a separate so-called allosteric site of each subunit. The ADPs each have an associated Mg2+, which is represented here by a ball of the same color as the ADP to which it binds.
+The first view, 1: PFK dimer, shows the two subunits in their R state conformation as represented by their Ca backbones with Subunit 1 in pink tint and Subunit 2 in pink. Two side chains in each subunit are shown, those of Glu 161 (red) and Arg 162 (cyan), which are part of the F6P binding site in the  T and R states, srespectively(see below). An F6P (hotpink) and an ADP (green; "ADP-active") are bound in the active site of each subunit. An additional ADP (yellow; "ADP-allo") is bound in a separate so-called allosteric site of each subunit. The ADPs each have an associated Mg2<sup>+</sup>, which is represented here by a ball of the same color as the ADP to which it binds.
 	Click the "ANIMATE" button to switch the dimer between its R and T states. In its T state, Subunit 1 is bluetint and Subunit 2 is skyblue. The side chains of Glu 161 and Arg 162 in both subunits are red and cyan as before (only the Ca and Cb atoms of the Arg 162 side chain in Subunit 1 are observed in the X-ray structure of the T state; those of Subunit 2 are all observed). The T state enzyme binds the inhibitor 2-phosphoglycolate (gold; "PGC"), a nonphysiological analog of the glycolytic intermediate phosphoenolpyruvate (PEP). Note that the binding site of PGC in the T state overlaps the allosteric binding site of ADP in the R state ("ADP-allo") and hence their binding is mutually exclusive. The T state active sites, which do not contain F6P, are marked by "ghost" F6Ps (gray;"F6P site"), which have the same positions as do the F6Ps in the R state enzyme.
-	The seconbd view, 2: Allo/Act Sites,  is a closeup of the upper portion of the first view showing both the active site and the allosteric site in this region. Note that the active site is located at the interface between two subunits and that the allosteric site interacts directly with the active site on the adjacent  subunit. Compare the R state and T state conformations by displaying both at once or clicking on "ANIMATE". Can you identify the Mg2+ ion associated with each of the ADPs bound to the enzyme in the R state? Which ADP atoms coordinate these Mg2+ ions?
+	The second view, 2: Allo/Act Sites,  is a closeup of the upper portion of the first view showing both the active site and the allosteric site in this region. Note that the active site is located at the interface between two subunits and that the allosteric site interacts directly with the active site on the adjacent subunit. Compare the R state and T state conformations by displaying both at once or clicking on "ANIMATE". Can you identify the Mg2<sup>+</sup> ion associated with each of the ADPs bound to the enzyme in the R state? Which ADP atoms coordinate these Mg2+ ions?
 	The phosphate group of PGC binds to the allosteric site in the T state in very nearly the same position that the beta phosphate group of "ADP-allo" binds to the R state allosteric site; both phosphate groups bind to the side chains of the same three residues (2 arg and 1 Lys; not shown).