Structural model of the TMH region of Ire1. (A) Configuration of a model TMH dimer obtained from atomistic MD simulations. Protomers are shown as an orange ribbon with the two F544 residues highlighted in red. POPC lipids and their phosphate moieties are shown in gray and purple, respectively. Cholesterol molecules and their hydroxyl groups are shown in light green and red, respectively. Water is shown with a transparent surface representation. (B) Membrane thickness around the sensor peptide, defined as the average vertical distance between the two phosphate layers. A representative structure of the dimeric TMH region is shown in blue. For the SEM of the thickness profile, see Fig. S4 C.