Zinc-finger proteins contain DNA-binding domains and have a wide variety of functions, most of which encompass some form of transcriptional activation or repression. The RING-type zinc finger motif is present in a number of viral and eukaryotic proteins and is made of a conserved cysteine-rich domain that is able to bind two zinc atoms. Proteins that contain this conserved domain are generally involved in the ubiquitination pathway of protein degradation. 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). ZNRF3 (Zinc/RING finger protein 3), also known as RNF203 (RING finger protein 203), is a 936 amino acid single pass transmembrane protein that contains one RING-type zinc finger. Related zinc/RING finger proteins, such as ZNRF1 and ZNRF2, are E3 ubiquitin-protein ligases that are thought to be involved in the establishment and maintenance of neuronal transmission and plasticity, therefore it is likely that ZNRF3 may function in a similar manner.