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. 2023 Nov 13;42(24):e114889. doi: 10.15252/embj.2023114889

Figure 1. Biochemical and structural characterization of the yeast Lac1‐Lip1 complex.

Figure 1

  1. Ceramide synthase (CerS) catalyzes ceramide formation via N‐acylation of a sphingoid base with a fatty acyl‐CoA. Dihydrosphingosine (DHS), a representative sphingoid base, was used to generate dihydroceramide in the activity assays in this study.
  2. Enzymatic activity of the wild‐type (WT) Lac1‐Lip1 complex and the catalytic mutant Lac1H255A/H256A‐Lip1 complex. Each data point is the average ± SEM of three independent experiments.
  3. CerS activity versus C26‐CoA concentration for the Lac1 alone protein and the Lac1‐Lip1 complex. The activity curve of the Lac1‐Lip1 complex follows an allosteric sigmoidal equation with a Khalf of 72.99 ± 1.44 μM for C26‐CoA and a V max of 475.7 ± 13.1 nmol/min/mg. Each data point is the average ± SEM of three independent experiments.
  4. Perpendicular views of the cryo‐EM map, overall structure, and electrostatic potential surface of the C26‐CoA‐bound Lac1‐Lip1 complex. Lac1 and Lip1 form a heterotetramer with a 2:2 stoichiometry. C26‐CoA lies inside the Lac1 subunit and traverses the lipid bilayer. The two Lac1 subunits are shown in wheat and light blue, respectively; the two Lip1 subunits are shown in light cyan and light green, respectively; C26‐CoA is shown in magenta. The two intramolecular disulfide bonds within Lip1 are shown in spheres. TM, transmembrane helix.

Source data are available online for this figure.