NEURL1B (neuralized homolog 1B), also known as neur2 or NEURL3, is a 555 amino acid protein that functions as an E3 ubiquitin-protein ligase. Involved in protein ubiquitination, NEURL1B contains two NHR (neuralized homology repeat) domains and one RING-type zinc finger. NEURL4 (neuralized homolog 4 (Drosophila)), also known as neuralized-like protein 4, is a 1,562 amino acid protein that is highly expressed in a wide variety of tissues. Containing six NHR (neuralized homology repeat) domains, NEURL4 exists as two alternatively spliced isoforms that are encoded by a gene that maps to human chromosome 17p13.1.