PHYS 402 |
| Phosphoglycerate kinase (PGK) is a single polypeptide (~45kDa) that catalyzes the reversible phospho-transfer reaction between ATP and 3-phosphoglycerate (3PG) to form ADP and 1,3-bis-phosphoglycerate. It has been proposed that phospho-transfer is facilitated by a hinge region in the enzyme that closes when both substrates are bound. Crystal structures and NMR data obtained on the ternary complexes of PGK from different sources have provided evidence from both the open and closed conformations. The conformation and activity of PGK is dependent on salt concentrations as well as bound substrates. We have performed biochemical studies that have confirmed activation of the phospho-transfer reaction occurs at low salt concentrations whereas high concentrations of salts inhibit activity. We used difference infrared to investigate how salt and pH influence protein structural changes associated with each of the PGK conformations. Previous studies from our lab have shown conformational changes due to substrate binding in higher salt conditions. Here we present new difference infrared data (PGK-ATP minus PGK, PGK-ADP minus PKG, PGK-ATP-3PG minus PGK, and PGK-ADP-3PG minus PKG) obtained at lower salt concentrations. The new data show unique vibrations are associated with nucleotide binding under the lower salt conditions. Additional studies found that pH also influences PGK activity and vibrational changes associated with nucleotide binding to PGK complexes. The infrared data indicate specific secondary structures and side chain conformations are associated with each of the PGK-nucleotide complexes. The data presented suggest that future infrared studies may ultimately help explain how salt and pH regulate substrate binding to PGK. |
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PHYS Poster Session - General Experiment
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Division of Physical Chemistry |