Molecular Dynamics Simulations Elucidate Conformational Dynamics Responsible for the Cyclization Reaction in TEAS

Area of Science:

• Biochemistry
• Molecular Biology
• Enzymology

Background:

• The Mg-dependent 5-epi-aristolochene synthase (TEAS) from Nicotiana tabacum catalyzes farnesyl pyrophosphate (FPP) to 5-epi-aristolochene.
• Previous studies proposed reaction mechanisms based on static structures, but substrate binding kinetics and protein dynamics remain unclear.

Purpose of the Study:

• To elucidate the substrate FPP binding kinetics and protein conformational dynamics in TEAS.
• To understand the role of specific residues and structural elements in the catalytic mechanism.

Main Methods:

• Extensive molecular dynamics simulations were employed.
• Analysis focused on loop conformation changes and crucial residue interactions.

Main Results:

• The noncatalytic NH2-terminal domain stabilizes key structural elements in the catalytic COOH-terminal domain.
• Induce-fit loop dynamics, triggered by Y527, optimize substrate binding in a U-shaped conformation.
• Mg(2+) coordination and residues W273, R264/R266, and Y527 are critical for stabilizing the substrate and facilitating catalysis.
• Protein dynamics play a more significant role than suggested by static crystal structures.

Conclusions:

• Protein conformational dynamics are essential for TEAS enzymatic activity.
• Findings provide insights into carbocation migration and electrophilic attack mechanisms.
• This study offers a guide for protein engineering to diversify sesquiterpene products for drug discovery.