- The nucleotide sequence for mouse calcitonin was determined from a cDNA obtained using a polymerase chain reaction (PCR) based method, the rapid amplification of cDNA ends (RACE)-PCR. Primers designed from highly conserved regions in the coding sequences of known rat and human calcitonin cDNAs were used to amplify calcitonin cDNA as 5'-end and 3'-end fragments from mouse thyroid RNA. The obtained cDNA is 850 bp in length most probably representing the entire mouse calcitonin mRNA. It contains an open reading frame coding for a 136 amino acid protein with a calculated M(r) of 15,143. Comparison of the deduced amino acid sequences of preprocalcitonin of mice with other species revealed highest homologies to the rat (93%) and human (77%) sequences. A recombinant form of mouse precalcitonin (rmPCT) of approximately 17 kDa was expressed as a fusion peptide in E.coli transformed with a PCR-cloned expression construct.