National Institutes of Health/National Institute of Mental Health (NIH/NIMH)
K99MH119591
米国
Other private
米国
引用
ジャーナル: Nat Commun / 年: 2024 タイトル: Structural and mechanistic insights into a lysosomal membrane enzyme HGSNAT involved in Sanfilippo syndrome. 著者: Boyang Zhao / Zhongzheng Cao / Yi Zheng / Phuong Nguyen / Alisa Bowen / Robert H Edwards / Robert M Stroud / Yi Zhou / Menno Van Lookeren Campagne / Fei Li / 要旨: Heparan sulfate (HS) is degraded in lysosome by a series of glycosidases. Before the glycosidases can act, the terminal glucosamine of HS must be acetylated by the integral lysosomal membrane enzyme ...Heparan sulfate (HS) is degraded in lysosome by a series of glycosidases. Before the glycosidases can act, the terminal glucosamine of HS must be acetylated by the integral lysosomal membrane enzyme heparan-α-glucosaminide N-acetyltransferase (HGSNAT). Mutations of HGSNAT cause HS accumulation and consequently mucopolysaccharidosis IIIC, a devastating lysosomal storage disease characterized by progressive neurological deterioration and early death where no treatment is available. HGSNAT catalyzes a unique transmembrane acetylation reaction where the acetyl group of cytosolic acetyl-CoA is transported across the lysosomal membrane and attached to HS in one reaction. However, the reaction mechanism remains elusive. Here we report six cryo-EM structures of HGSNAT along the reaction pathway. These structures reveal a dimer arrangement and a unique structural fold, which enables the elucidation of the reaction mechanism. We find that a central pore within each monomer traverses the membrane and controls access of cytosolic acetyl-CoA to the active site at its luminal mouth where glucosamine binds. A histidine-aspartic acid catalytic dyad catalyzes the transfer reaction via a ternary complex mechanism. Furthermore, the structures allow the mapping of disease-causing variants and reveal their potential impact on the function, thus creating a framework to guide structure-based drug discovery efforts.
unsharpened map used to dock TM1 (residue 191-226). All other areas are built based on the sharpened map. The entire model is refined against the sharpened map.