Members of this family adopt a coiled coil structure, with two antiparallel alpha-helices that are tightly strapped together by two disulfide bridges at each end. The protein sequence shows a cysteine motif, required for the stabilisation of the coiled-coil-like structure. Additional inter-helix hydrophobic contacts impart stability to this scaffold. The precise function of this eukaryotic domain is, as yet, unknown. MTCP1 is found in mitochondria. Mature-T-Cell Proliferation) is the first gene unequivocally identified in the group of uncommon leukemias with a mature phenotype.