The CBP tag, or calmodulin binding peptide tag, is a commonly used epitope attached to the N- or C- termini of recombinant proteins. The CBP peptide binds specifically to calmodulin, allowing for the affinity purification of tagged fusion proteins with calmodulin resin. The sequence is 26-28 amino acids in length, comprising KRRWKKNFIAVSAANRFKKISSSGAL. Antibodies targeting the CBP epitope may be a useful tool in immunological investigations of CBP-tagged proteins.