Structural dynamics of yeast hexokinase during catalysis.

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Yeast hexokinase is a key enzyme in glucose metabolism.
• Enzyme conformational changes are vital for catalysis and regulation.
• Understanding hexokinase's structure-activity relationship is essential.

Purpose of the Study:

• To elucidate the structural basis of substrate-induced conformational changes in yeast hexokinase.
• To determine the role of these changes in enzyme catalysis and control.
• To resolve the structure of the hexokinase ternary complex.

Main Methods:

• High-resolution X-ray crystallography of yeast hexokinase.
• Crystallization in the presence and absence of substrates (glucose, xylose, ADP).
• Low-resolution structure determination.
• Crystallographic refinement at 2.1 Å resolution.
• Chemical sequencing of tryptic peptides.

Main Results:

• Glucose binding induces a substantial conformational change, closing the enzyme's active site cleft.
• The enzyme crystallized with xylose and ADP is in an 'open' conformation, not a ternary complex.
• High-resolution structural data is being integrated with protein sequence information.

Conclusions:

• Substrate binding causes significant domain closure in yeast hexokinase, essential for its function.
• The study provides insights into the mechanism of substrate-induced conformational changes in kinases.
• Further structural and sequence data will detail the enzymatic mechanism and regulatory roles.