Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.2.19 (ubiquitin-protein ligase)
 799 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In the yeast Saccharomyces cerevisiae, the Apg12p-Apg5p conjugating system is essential for autophagy. Apg7p is required for the conjugation reaction, because Apg12p is unable to form a conjugate with Apg5p in the apg7/cvt2 mutant. Apg7p shows a significant similarity to a ubiquitin-activating enzyme, Uba1p. In this article, we investigated the function of Apg7p as an Apg12p-activating enzyme. Hemagglutinin-tagged Apg12p was coimmunoprecipitated with c-myc-tagged Apg7p. A two-hybrid experiment confirmed the interaction. The coimmunoprecipitation was sensitive to a thiol-reducing reagent. Furthermore, a thioester conjugate of Apg7p was detected in a lysate of cells overexpressing both Apg7p and Apg12p. These results indicated that Apg12p interacts with Apg7p via a thioester bond. Mutational analyses of Apg7p suggested that Cys507 of Apg7p is an active site cysteine and that both the ATP-binding domain and the cysteine residue are essential for the conjugation of Apg7p with Apg12p to form the Apg12p-Apg5p conjugate. Cells expressing mutant Apg7ps, Apg7pG333A, or Apg7pC507A showed defects in autophagy and cytoplasm-to-vacuole targeting of aminopeptidase I. These results indicated that Apg7p functions as a novel protein-activating enzyme necessary for Apg12p-Apg5p conjugation.
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PMID:Apg7p/Cvt2p: A novel protein-activating enzyme essential for autophagy. 1023 50

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.
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PMID:Apg10p, a novel protein-conjugating enzyme essential for autophagy in yeast. 1050 57