A cyclophilin-related protein involved in the function of natural killer cells.

Natural killer cells are non-major histocompatibility complex-restricted large granular lymphocytes that can recognize and destroy tumor cells without prior stimulation. A 150-kDa molecule on the surface of human natural killer cells was identified as a component of a putative tumor-recognition complex. We report here the isolation of cDNAs coding for the 150-kDa tumor-recognition molecule from human and mouse cDNA libraries. The amino terminus of the predicted protein contains a large hydrophobic region followed by a domain that is highly homologous to cyclophilin/peptidylprolyl cis-trans isomerase. The remainder of the protein is extremely hydrophilic and contains three homologous positively charged clusters. There are also three regions that contain extensive arginine- and serine-rich repeats. Comparison of the human and mouse predicted amino acid sequences revealed > 80% homology.