Subunit communication in the anthranilate synthase complex from Salmonella typhimurium

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• The anthranilate synthase-phosphoribosyl transferase complex is crucial for tryptophan biosynthesis in Salmonella typhimurium.
• This heterotetrameric enzyme (TrpE2-TrpD2) exhibits allosteric properties and feedback inhibition by L-tryptophan.

Purpose of the Study:

• To investigate the communication between regulatory and catalytic sites on different subunits of the tryptophan synthase complex.
• To understand how L-tryptophan binding to one subunit influences the activity of other subunits.

Main Methods:

• In vitro assembly of a hybrid enzyme complex using catalytically active and inactive mutant TrpE subunits.
• Characterization of the hybrid complex to analyze subunit communication and allosteric regulation.

Main Results:

• The hybrid complex demonstrated that a single L-tryptophan molecule binding to one TrpE subunit is sufficient to induce conformational changes.
• These conformational changes propagate to the companion subunit, affecting its active site and demonstrating inter-subunit communication.

Conclusions:

• The study elucidates the mechanism of allosteric regulation in the tryptophan synthase complex.
• Evidence supports efficient signal transduction between regulatory and catalytic sites within the heterotetrameric enzyme.