P24 protein family is a group of transmembrane proteins that are major components of COPI and COPII-coated vesicles. The family is also known as EMP24/GP25L/p24 family and TMP21-like proteins. The latter naming was after transmembrane emp24 domain-containing protein 10 that was found in the human brain. It was claimed to block the beta-amyloid peptide, which is implicated in the pathogenesis of Alzheimer's disease. p24 family proteins localize to the major organelles of the early secretory pathway: the endoplasmic reticulum and the Golgi apparatus, where they seem to be involved in trafficking between the two compartments. In yeast, all p24 family proteins can be removed, causing only a mild phenotype. However, in mammals at least some p24 proteins are essential for survival, e.g. removal of p24δ1 is lethal in mice. p24 family members have been implicated in the biogenesis of COPI and COPII-coated vesicles, transporting membrane-bound proteins through the secretory system, and forming the structure of the endoplasmic reticulum and Golgi.