Lipid droplet targeting drives substrate access during very long chain fatty acid activation by Fat1.

Lipid droplets serve as the site of VLCFA activation by Fat1, with VLCFAs preferentially partitioning into LDs and Fat1 targeting LD surfaces via an amphipathic helix.

• Why it matters: Understanding where and how VLCFA activation occurs is crucial because these highly hydrophobic molecules are essential precursors for yeast ceramides, yet their activation site was previously unresolved.
• What they did: The study used molecular simulations, in vitro reconstitutions, and structural predictions to show that VLCFAs accumulate in LDs, and Fat1 targets LD surfaces through an N-terminal amphipathic helix, with an essential hydrophobic cavity connecting the active site to the membrane.
• The result: This model clarifies how Fat1's organelle targeting aligns with the biophysical properties of VLCFAs, enabling direct shuttle from LD core into the enzyme's pocket, advancing understanding of fatty acid activation mechanisms.