Figure 1. Crystal structure of an open Sec14p conformer.

The Sec14p fold is comprised of twelve α-helices, six β-strands and eight 3₁₀ helices. The hydrophobic pocket is formed by six β-strands and three α-helices (helices α8, α9 and α11; in grey) and this pocket is predicted to be gated by the A₁₀/T₄ helix (in blue). The lipid binding pocket of apo-Sec14p is occupied by 2 molecules of β-octylglucoside (in yellow) and these molecules are oriented such that the acyl chains project into the pocket, disposing the headgroup towards solvent. The N-terminal α1, α2, α3 and α4 helices form the “tripod motif” that helps target Sec14p to Golgi membranes (in green). The “string motif” (in red) is comprised of a random coil regions and four 3₁₀ helices. This structural element wraps around the back of the lipid binding domain and is critical both for protein stability and the conformational dynamics that accompany the phospholipid exchange cycle.