Background
The enzymes of the NEDDylation pathway play a pivotal role in the activation of the largest class of ubiquitin E3 ligases called Cullin RING Ligases (CRLs). Akin to ubiquitylation three classes of enzymes are involved in the process of mammalian NEDDylation; E1 activating enzyme (APP-BP1/UBA3 heterodimer), E2 conjugating enzymes (UBE2F or UBE2M) and E3 ligases (Meyer-Schaller, et al., 2009) including the Domain Containing Like Protein1 (DCNL1) and Ring Box 1(RBX1) heterodimer (Huang et al., 2011; Morimoto et al., 2003). Neural Precursor Cell Expressed, Developmentally Downregulated 8 (NEDD8) is a member of the ubiquitin like modifiers and the human gene was first described by (Kamitani, et al., 1997). The heterodimeric E1, APP-BP1/UBA3 forms a complex in vitro and a thioester linkage with NEDD8 (Osaka et al., 1998). NEDD8 has also been co-crystallised with APP-BP1 and ATP (Walden et al., 2003). The structure consists of an E1-specific domain organised around a catalytic cysteine and a domain involved in E2 recognition which coordinates protein binding and drives the E1's reactions. This ATP-dependent activation of NEDD8 enables its transfer via a transthiolation reaction to either of the NEDD8 E2 conjugating enzymes UBE2F or UBE2M. Subsequently the NEDD8 is conjugated onto the cullin subunit of the CRL. This has been shown to occur through N-terminal acetylation of the E2 conjugating enzyme Ube2M and burial of the N-acetyl- methionine of Ube2M into a hydrophobic pocket of Defective in Cullin Neddylation 1 (DCNL1) which promotes an E3 dependent Neddylation of Cullin1 (Scott et al., 2011).
References
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Kamitani T, Kito K, Nguyen HP, Yeh E.T. (1997) Characterization of NEDD8, a developmentally down-regulated ubiquitin-like protein, J Biol Chem, 272, 28557-28562.
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