[2] Many processes such as cell division, immune responses and embryonic development are also regulated by post-translational modification by ubiquitin and ubiquitin-like proteins.

[4] In the next step a catalytic cysteine (Figure 3) on the E1 enzyme attacks the ubiquitin-AMP complex through acyl substitution, simultaneously creating a thioester bond and an AMP leaving group.

The function of the secondary ubiquitin remains largely unknown, however it is believed that it may facilitate conformational changes seen in the E1 enzyme during the transthioesterification process.

[2] The following genes encode ubiquitin-activating enzymes: The ubiquitin-proteasome system is critical to appropriate protein degradation within cells.

In brevity, UBE1 missense may lead to a disturbed complex building with gigaxonin, a protein involved in axonal structure and neuronal maintenance.