Isolation of two cDNA sequences which encode cytotoxic cell proteases

Two cDNAs which cross-hybridized with cytotoxic cell protease genes were identified in a library generated from a cytotoxic T cell line. Sequence analysis revealed that the two new members of the family contained the three catalytic triad residues which characterize the active sites of serine proteases. A comparison of the protein sequences revealed not only a high degree of homology but also the conservation of some unusual structural features. These include the lack of a disulphide bond which spans the active site serine, the presence of a signal sequence and the inference of a dipeptide activation sequence.