Suzuki T, Park H, Hollingsworth N M, Sternglanz R, Lennarz W J
Department of Biochemistry and Cell Biology, Institute of Cell and Developmental Biology, State University of New York at Stony Brook, Stony Brook, New York 11794-5215, USA.
J Cell Biol. 2000 May 29;149(5):1039-52. doi: 10.1083/jcb.149.5.1039.
It has been proposed that cytoplasmic peptide:N-glycanase (PNGase) may be involved in the proteasome-dependent quality control machinery used to degrade newly synthesized glycoproteins that do not correctly fold in the ER. However, a lack of information about the structure of the enzyme has limited our ability to obtain insight into its precise biological function. A PNGase-defective mutant (png1-1) was identified by screening a collection of mutagenized strains for the absence of PNGase activity in cell extracts. The PNG1 gene was mapped to the left arm of chromosome XVI by genetic approaches and its open reading frame was identified. PNG1 encodes a soluble protein that, when expressed in Escherichia coli, exhibited PNGase activity. PNG1 may be required for efficient proteasome-mediated degradation of a misfolded glycoprotein. Subcellular localization studies indicate that Png1p is present in the nucleus as well as the cytosol. Sequencing of expressed sequence tag clones revealed that Png1p is highly conserved in a wide variety of eukaryotes including mammals, suggesting that the enzyme has an important function.
有人提出，细胞质肽：N-聚糖酶（PNGase）可能参与了蛋白酶体依赖性质量控制机制，该机制用于降解在内质网中未能正确折叠的新合成糖蛋白。然而，由于缺乏关于该酶结构的信息，我们深入了解其精确生物学功能的能力受到了限制。通过筛选诱变菌株文库，以寻找细胞提取物中缺乏PNGase活性的菌株，从而鉴定出一个PNGase缺陷型突变体（png1-1）。通过遗传学方法将PNG1基因定位到第十六条染色体的左臂，并确定了其开放阅读框。PNG1编码一种可溶性蛋白，该蛋白在大肠杆菌中表达时表现出PNGase活性。PNG1可能是蛋白酶体介导的错误折叠糖蛋白高效降解所必需的。亚细胞定位研究表明，Png1p存在于细胞核和细胞质中。表达序列标签克隆的测序显示，Png1p在包括哺乳动物在内的多种真核生物中高度保守，这表明该酶具有重要功能。
