May play a role in anterograde transport of membrane proteins from the endoplasmic reticulum to the Golgi. May be involved in CASP8-mediated apoptosis (By similarity). Homodimer and heterodimer with BCAP31. Binds CASP8 as a complex containing BCAP31, BCAP29, BCL2 and/or BCL2L1. Interacts with VAMP3, VAMP1 and membrane IgD immunoglobulins. May interact with ACTG1 and non-muscle myosin II (By similarity). Highly expressed in brain and testis; detected at lower levels in thymus, spleen, liver, lung and bone marrow. Belongs to the BCAP29/BCAP31 family.