Substrate binding to phosphoglycerate kinase monitored by 1-anilino-8-naphthalenesulfonate

Area of Science:

• Biochemistry
• Enzyme kinetics
• Structural biology

Background:

• Yeast phosphoglycerate kinase (PGK) is a crucial enzyme in glycolysis.
• Understanding PGK's structure-function relationship is vital for metabolic studies.
• 1-anilino-8-naphthalenesulfonate (ANS) is a fluorescent probe used to study protein structure.

Purpose of the Study:

• To investigate the interaction between ANS and yeast phosphoglycerate kinase.
• To utilize ANS as a probe for studying PGK's structure and function.
• To characterize the binding kinetics and conformational changes induced by ANS and substrates.

Main Methods:

• Kinetic assays to determine enzyme inhibition.
• Equilibrium dialysis to assess binding affinity.
• Fluorometric titrations to monitor ANS fluorescence changes and binding sites.

Main Results:

• ANS inhibits yeast phosphoglycerate kinase activity, with a Ki of 1-2 mM.
• ANS binding is competitive with MgATP and noncompetitive with 3-phosphoglycerate at the primary site.
• ANS binding increases fluorescence and causes a blue shift, indicating interaction with a hydrophobic site; substrate binding induces further fluorescence changes.

Conclusions:

• ANS serves as an effective fluorescent probe for yeast phosphoglycerate kinase.
• The enzyme possesses multiple inhibitor sites for ANS, with the primary site exhibiting complex binding kinetics.
• ANS binding and substrate interactions reveal significant conformational dynamics of phosphoglycerate kinase.