Marginal zone B- and B1-cell-specific protein (MZB1)

Associates with immunoglobulin M (IgM) heavy and light chains and promotes IgM secretion and assembly. May exert its effect by acting as a molecular chaperone or as an oxidoreductase as it displays a low level of oxidoreductase activity (By similarity).

Isoform 2 may be involved in regulation of apoptosis. Helps to diversify peripheral B-cell functions by regulating Ca(2+) stores, antibody secretion and integrin activation.