Shintani T, Mizushima N, Ogawa Y, Matsuura A, Noda T, Ohsumi Y
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
EMBO J. 1999 Oct 1;18(19):5234-41. doi: 10.1093/emboj/18.19.5234.
Autophagy is a cellular process for bulk degradation of cytoplasmic components. The attachment of Apg12p, a modifier with no significant similarity to ubiquitin, to Apg5p is crucial for autophagy in yeast. This reaction proceeds in a ubiquitination-like manner, and requires Apg7p and Apg10p. Apg7p exhibits a considerable similarity to ubiquitin-activating enzyme (E1) and is found to activate Apg12p with ATP hydrolysis. Apg10p, on the other hand, shows no significant similarity to other proteins whose functions are known. Here, we show that after activation by Apg7p, Apg12p is transferred to the Cys-133 residue of Apg10p to form an Apg12p-Apg10p thioester. Cells expressing Apg10p(C133S) do not generate the Apg12p-Apg5p conjugate, which leads to defects in autophagy and cytoplasm-to-vacuole targeting of aminopeptidase I. These findings indicate that Apg10p is a new type of protein-conjugating enzyme that functions in the Apg12p-Apg5p conjugation pathway.
自噬是一种对细胞质成分进行大量降解的细胞过程。Apg12p是一种与泛素无显著相似性的修饰因子，它与Apg5p的连接对于酵母中的自噬至关重要。该反应以类似泛素化的方式进行，并且需要Apg7p和Apg10p。Apg7p与泛素激活酶（E1）具有相当大的相似性，并且被发现可通过ATP水解激活Apg12p。另一方面，Apg10p与其他已知功能的蛋白质没有显著相似性。在此，我们表明在被Apg7p激活后，Apg12p转移至Apg10p的Cys-133残基上，形成Apg12p-Apg10p硫酯。表达Apg10p（C133S）的细胞不会产生Apg12p-Apg5p共轭物，这导致自噬缺陷以及氨肽酶I从细胞质到液泡的靶向运输缺陷。这些发现表明Apg10p是一种新型的蛋白质共轭酶，在Apg12p-Apg5p共轭途径中发挥作用。
