LAM proteins contain one or two StARkin domains (SD1 and SD2), which bind sterols. These domains move between membranes, enabled by flexible linkers. LAM2 and LAM4 are anchored to the endoplasmic reticulum (ER) membrane, and connect to the plasma membrane via specific membrane-localized proteins. New structure studies show that the StARkin domains of LAM2 and LAM4 resemble a cup containing sterol, with a partially-closed lid—sterols bind near the top of the cavity, possibly enabling sterols to slip quickly in and out. Image credit: figure published in this PNAS paper.