Band 3 protein fragments are phylogenetically preserved transport peptides located on the organelle membranes especially the erythrocyte membrane where they mediate anion exchange1.

Band 3 peptides were originally identified following SDS-gel electrophoresis of erythrocyte cell membrane. The large third band on the gel turned out to be the peptide. Hence the name Band 31.

Band 3 proteins are members of anion-exchange (AE) family of proteins2. AE proteins are encoded by a multigene family that has atleast three genes, AE1, AE2, AE3 and several splicioforms2. They are all expressed by most cells, e.g., erythrocytes, cardiomyocytes.