Structural basis for catalysis and substrate specificity of human ACAT1. Author Hongwu Qian, Xin Zhao, Renhong Yan, Xia Yao, Shuai Gao, Xue Sun, Ximing Du, Hongyuan Yang, Catherine Wong, Nieng Yan Publication Year 2020 Type Journal Article Abstract As members of the membrane-bound O-acyltransferase (MBOAT) enzyme family, acyl-coenzyme A:cholesterol acyltransferases (ACATs) catalyse the transfer of an acyl group from acyl-coenzyme A to cholesterol to generate cholesteryl ester, the primary form in which cholesterol is stored in cells and transported in plasma. ACATs have gained attention as potential drug targets for the treatment of diseases such as atherosclerosis, Alzheimer's disease and cancer. Here we present the cryo-electron microscopy structure of human ACAT1 as a dimer of dimers. Each protomer consists of nine transmembrane segments, which enclose a cytosolic tunnel and a transmembrane tunnel that converge at the predicted catalytic site. Evidence from structure-guided mutational analyses suggests that acyl-coenzyme A enters the active site through the cytosolic tunnel, whereas cholesterol may enter from the side through the transmembrane tunnel. This structural and biochemical characterization helps to rationalize the preference of ACAT1 for unsaturated acyl chains, and provides insight into the catalytic mechanism of enzymes within the MBOAT family. Keywords Humans, Substrate Specificity, Models, Molecular, Biocatalysis, Protein Multimerization, Catalytic Domain, Cryoelectron Microscopy, Sterol O-Acyltransferase Journal Nature Volume 581 Issue 7808 Pages 333-338 Date Published 2020 May ISSN Number 1476-4687 DOI 10.1038/s41586-020-2290-0 Alternate Journal Nature PMCID 5093084 PMID 32433614 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML