Ichimura Y, Kirisako T, Takao T, Satomi Y, Shimonishi Y, Ishihara N, Mizushima N, Tanida I, Kominami E, Ohsumi M, Noda T, Ohsumi Y
Department of Cell Biology, National Institute for Basic Biology, Okazaki, Japan.
Nature. 2000 Nov 23;408(6811):488-92. doi: 10.1038/35044114.
Autophagy is a dynamic membrane phenomenon for bulk protein degradation in the lysosome/vacuole. Apg8/Aut7 is an essential factor for autophagy in yeast. We previously found that the carboxy-terminal arginine of nascent Apg8 is removed by Apg4/Aut2 protease, leaving a glycine residue at the C terminus. Apg8 is then converted to a form (Apg8-X) that is tightly bound to the membrane. Here we report a new mode of protein lipidation. Apg8 is covalently conjugated to phosphatidylethanolamine through an amide bond between the C-terminal glycine and the amino group of phosphatidylethanolamine. This lipidation is mediated by a ubiquitination-like system. Apg8 is a ubiquitin-like protein that is activated by an E1 protein, Apg7 (refs 7, 8), and is transferred subsequently to the E2 enzymes Apg3/Aut1 (ref. 9). Apg7 activates two different ubiquitin-like proteins, Apg12 (ref. 10) and Apg8, and assigns them to specific E2 enzymes, Apg10 (ref. 11) and Apg3, respectively. These reactions are necessary for the formation of Apg8-phosphatidylethanolamine. This lipidation has an essential role in membrane dynamics during autophagy.
自噬是一种在溶酶体/液泡中进行大量蛋白质降解的动态膜现象。Apg8/Aut7是酵母自噬的一个必需因子。我们之前发现，新生Apg8的羧基末端精氨酸被Apg4/Aut2蛋白酶去除，在C末端留下一个甘氨酸残基。然后Apg8转化为一种与膜紧密结合的形式（Apg8-X）。在此我们报道一种新的蛋白质脂化模式。Apg8通过C末端甘氨酸与磷脂酰乙醇胺的氨基之间的酰胺键与磷脂酰乙醇胺共价结合。这种脂化由一个类泛素化系统介导。Apg8是一种类泛素蛋白，被E1蛋白Apg7激活（参考文献7、8），随后被转移至E2酶Apg3/Aut1（参考文献9）。Apg7激活两种不同的类泛素蛋白，Apg12（参考文献10）和Apg8，并分别将它们分配给特定的E2酶，Apg10（参考文献11）和Apg3。这些反应对于Apg8-磷脂酰乙醇胺的形成是必需的。这种脂化在自噬过程中的膜动态变化中起重要作用。
