Cholesterol-binding START domain of mammalian STARD1 and related proteins
This subgroup includes the steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domains of STARD1 (also known as StAR) and related proteins. It belongs to the START domain family, and in turn to the SRPBCC (START/RHO_alpha_C/PITP/Bet_v1/CoxG/CalC) domain superfamily of proteins that bind hydrophobic ligands. SRPBCC domains have a deep hydrophobic ligand-binding pocket. STARD1 has a high affinity for cholesterol. It can reduce macrophage lipid content and inflammatory status. It plays an essential role in steroidogenic tissues: transferring the steroid precursor, cholesterol, from the outer to the inner mitochondrial membrane, across the aqueous space. Mutations in the gene encoding STARD1/StAR can cause lipid congenital adrenal hyperplasia (CAH), an autosomal recessive disorder characterized by a steroid synthesis deficiency and an accumulation of cholesterol in the adrenal glands and the gonads.