Ubiquitin is a 76 amino acid protein weighing approximately 8kDa. Although most notorious for its role in proteasomal degradation, it also plays a pivotal role in an array of additional signaling processes such as protein trafficking, endocytosis, autophagy, immune signaling, DNA damage response, cell cycle control, epigenetic regulation, and many others. Here, we detail the molecular mechanism of one of more understudies RBR E3 ligases, RNF216, as well as verify substrates of the more well studied RBR E3 ligase Parkin. We also investigate the molecular underpinnings of HECT E3 ligase Rsp5 and its substrate Hsp104 and briefly confer a literature review of heterodimeric RING E3 BRCA1/BARD1 and note a large literature gap in this E3. A deep literature review regarding the mechanisms of each type of E3 ligase prepares us to draw conclusions based on verified data obtained by using the YIN lab’s Orthogonal Ubiquitin Transfer (OUT) cascade and put these results into the context of the structural mechanisms of these E3 ubiquitin ligases.