Ubiquitination is an important mechanism through which three classes of enzymes act in concert to target short-lived or abnormal proteins for destruction. The three classes of enzymes involved in ubiquitination are the ubiquitin-activating enzymes (E1s), the ubiquitin-conjugating enzymes (E2s) and the ubiquitin-protein ligases (E3s). MARCH3 (membrane-associated ring finger (C3HC4) 3), also known as RNF173, is a 253 amino acid multi-pass membrane protein that localizes to cytoplasmic vesicles and early endosomes and contains one RING-CH-type zinc finger. Involved in the pathway of protein modification, MARCH3 functions as an E3 ubiquitin-protein ligase that accepts a ubiquitin residue from an E2 ubiquitin-conjugating enzyme and is thought to be involved in endosomal trafficking events.