Protein degradation: Two main mechanisms are involved in protein digestion, namely the lysosome — autophagy system and the proteasome — ubiquitin system [121]. (biochemj.org)
Because all the itchy mice had a defective version of the E3 ligase, Copeland suspects that their ubiquitin systems fail to tag immune - related defense proteins or foreign substances called antigens for disposal — both of which then might pile up and attract too many helper macrophages to the scene, wreaking havoc with the immune response. (sciencemag.org)
Like many viruses, MERS works by hijacking the ubiquitin system in human cells composed of hundreds of proteins that rely on ubiquitin to keep the cells alive and well. (sciencedaily.com)