Structure of the yeast ceramide synthase

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Ceramides are vital lipids crucial for sphingolipid synthesis and cellular signaling.
• Ceramide synthases (CerS) catalyze ceramide production via N-acylation.
• The structural and mechanistic details of CerS enzymes were previously unknown.

Purpose of the Study:

• To determine the high-resolution structure of the yeast ceramide synthase complex.
• To elucidate the catalytic mechanism and substrate binding of CerS.
• To understand the inhibition mechanism of fumonisin B1.

Main Methods:

• Cryo-electron microscopy single-particle analysis was employed.
• The structure of the yeast CerS complex was determined in active and inhibited states.
• Fumonisin B1 inhibition was analyzed structurally.

Main Results:

• The yeast CerS complex structure revealed a dimer of Lip1 subunits associated with catalytic Lag1 and Lac1 subunits.
• A hydrophobic tunnel connecting the cytosol to the intermembrane space was identified within each catalytic subunit.
• The active site was visualized in a substrate-bound intermediate state, and fumonisin B1 was shown to bind competitively within the acyl-CoA tunnel.

Conclusions:

• The study provides unprecedented structural insights into ceramide synthase function.
• The findings elucidate the mechanism of ceramide synthesis and fumonisin B1 inhibition.
• This structural information is key for understanding sphingolipid metabolism and developing targeted inhibitors.