Characterization of cDNA for murine tripeptidyl-peptidase II reveals alternative splicing.

Tripeptidyl-peptidase II (TPP II) is a cytosolic high-M(r) exopeptidase with an active site of the subtilisin type. This paper describes cloning of cDNA encoding murine TPP II. Four clones were isolated from a murine mastocytoma cDNA library and the 5'-end was isolated by use of 5'-RACE (rapid amplification of cDNA ends). A total of 4611 bp were isolated, including the complete coding region. The deduced amino acid sequence shows a 96% overall identity when compared with the previously cloned human TPP II. The remarkably high identity indicates that not only the catalytic domain, but almost the entire subunit, must be of functional importance. Alignment with subtilisin-like serine peptidases identified Asp44, His264 and Ser449 as the catalytic triad, thus defining an extra domain of approximately 200 amino acids between the catalytic Asp and His in TPP II as compared with other subtilases. In addition, it was demonstrated that different polyadenylation signals can be utilized, since two different clones with untranslated 3'-ends of 155 bp and 781 bp respectively have been isolated. Finally, one of the isolated clones contains an extra 39 bp insert encoding 13 amino acids, which implies alternative splicing of the mRNA.