聚糖
磷酸化
生物化学
酶
甘露糖
水解酶
磷酸转移酶
活动站点
化学
蛋白质亚单位
糖基化
酶激活剂
结合位点
生物
细胞生物学
糖蛋白
基因
作者
Hua Li,Wang-Sik Lee,Xinwei Feng,Lin Bai,Benjamin C. Jennings,Lin Liu,Balraj Doray,William M. Canfield,Stuart Kornfeld,Li H
标识
DOI:10.1038/s41594-022-00748-0
摘要
Vertebrates use the mannose 6-phosphate (M6P)-recognition system to deliver lysosomal hydrolases to lysosomes. Key to this pathway is N-acetylglucosamine (GlcNAc)-1-phosphotransferase (PTase) that selectively adds GlcNAc-phosphate (P) to mannose residues of hydrolases. Human PTase is an α2β2γ2 heterohexamer with a catalytic core and several peripheral domains that recognize and bind substrates. Here we report a cryo-EM structure of the catalytic core of human PTase and the identification of a hockey stick-like motif that controls activation of the enzyme. Movement of this motif out of the catalytic pocket is associated with a rearrangement of part of the peripheral domains that unblocks hydrolase glycan access to the catalytic site, thereby activating PTase. We propose that PTase fluctuates between inactive and active states in solution, and selective substrate binding of a lysosomal hydrolase through its protein-binding determinant to PTase locks the enzyme in the active state to permit glycan phosphorylation. This mechanism would help ensure that only N-linked glycans of lysosomal enzymes are phosphorylated. Cryo-EM analysis reveals that human PTase α/β subunit has a well-ordered catalytic core and flexible peripheral domains that contain a hockey stick-like motif, which moves in and out of the catalytic pocket to control the enzyme activation.
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