Nucleotide sequence of bovine prochymosin cDNA and the mechanism of cDNA deletion.

A plasmid pTLC23 harbouring entire cDNA sequence coding for prochymosin was constructed from clones pCT5 and pCT15. The nucleotide sequence of the complete cDNA insert, determined by using dideoxy sequencing method, indicates that the cloned DNA apparently represents the coding sequence for prochymosin B. Based on the data presented here, the differences between the DNA sequences reported by Nishimori et al., Harris et al. and Moir et al. were discussed as well. DNA sequence analysis reveals that the deletion in pCT15 covers positions 862-960. The missing sequence is characterized as an entire exon between intron G and intron H of the prochymosin gene, and by ending with splicing signal AG, it is suggested that the deletion in middle region of coding sequence results from the incorrect splicing of pre-mRNA.