B cell maturation protein (BCMA) is a type III membrane protein which belongs to the TNF receptor superfamily (TNFRSF17). BCMA contains one extracellular cysteine rich domain, as well as TACI. Human BCMA is a 184 amino acid (aa) protein consisting of a 54 aa extracellular domain, a 23 aa transmembrane domain, and a 107 aa intracellular domain. Mouse and human BCMA share 62% amino acid identity. BCMA is mainly expressed in immune organs and mature B cell lines. BCMA appears to be localized to the Golgi compartment. BCMA may play an important role in B cell development, function and regulation.