CHARACTERIZATION OF CDNA FOR MURINE TRIPEPTIDYL-PEPTIDASE-II REVEALS ALTERNATIVE SPLICING

Tripeptidyl-peptidase II (TPP II) is a cytosolic high-M(r) exopeptidas e with an active site of the subtilisin type. This paper describes clo ning 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 is olated, including the complete coding region. The deduced amino acid s equence 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 f unctional importance. Alignment with subtilisin-like serine peptidases identified Asp(44), His(264) and Ser(449) as the catalytic triad, thu s defining an extra domain of similar to 200 amino acids between the c atalytic Asp and His in TPP II as compared with other subtilases. In a ddition, it was demonstrated that different polyadenylation signals ca n be utilized, since two different clones with untranslated 3'-ends of 155 bp and 781 bp respectively have been isolated. Finally, one of th e isolated clones contains an extra 39 bp insert encoding 13 amino aci ds, which implies alternative splicing of the mRNA.