Breast and Kidney-expressed chemokine (BRAK) is a CXC chemokine expressed in normal tissue in the absence of inflammatory stimuli, and infrequently expressed in cancer cell lines. BRAK is known to be a highly selective monocyte chemoattractant.However, main function and receptor selectivity is unknown at this time.BRAK contains the four highly conserved cysteine residues present in CXC chemokines.The sequence of the mature protein consists of 87 amino acid residues, and is approximately 30% homologous to the sequences of MIP-2 α and β.Recombinant human BRAK is a 9.4 kDa protein containing 77 amino acid residues.