The BI-1 (Bax inhibitor 1) family is evolutionarily conserved as integral membrane proteins containing multiple membrane-spanning domains that are predominantly localized to intracellular membranes. BI-1 family members share multiple motifs and transcriptional factors within the promoter and the coding regions. They represent regulators of cell death pathways and are highly conserved in evolution from plants to insects, amphibians, mammals and pox-viruses. GAAP (Golgi anti-apoptotic protein), also known as TMBIM4 (transmembrane Bax inhibitor motif containing 4), S1R, ZPRO or CGI-119, is a 238 amino acid multi-pass membrane protein that belongs to the BI-1 family. Ubiquitously expressed, GAAP inhibits apoptosis induced by intrinsic and extrinsic apoptotic stimuli.