Multiple forms of rat calpastatin cDNA in the coding region of functionally unknown amino-terminal domain

Partial mouse and rat calpastatin cDNAs containing functionally unknown amino-terminal regions were cloned by the polymerase chain reaction (PCR) method. Two types of clones were obtained for the rat calpastatin; one had a sequence similar to mouse and human calpastatins, while the other had a deletion of 38 amino acid residues in this region. Both types of the rat sequence differed from the previously reported rat calpastatin which had additional deletions. The occurrence of multiple forms of calpastatin suggests alternative splicing in the functionally unknown domain.