Updated project metadata. To provide structural insights into the mechanism of the specific association of the coactivator MED1 with the Vitamin D nuclear (VDR)-RXR heterodimer, we used combined structural methods including X-ray crystallography, small angle X-ray scattering (SAXS), NMR, hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS), crosslinking mass spectrometry as well as biophysical methods.