Cloning and characterization of a cDNA for rat tissue-type plasminogen activator

Two partly overlapping lambda gt11 cDNA clones coding for the 22S rat tissue-type plasminogen activator (t-PA) mRNA were isolated. The cDNA sequences cover 2445 nucleotides of the mRNA, including a 5' untranslated region of 31 nucleotides, an open reading frame of 1677 nucleotides, a 3' untranslated region of 737 nucleotides, and a poly(A) tail. The open reading frame codes for a 17-amino-acid signal peptide, a propeptide with 12 amino acids, and the mature protein with 530 amino acids. Rat t-PA has 81% and 92% amino acid sequence identity with the human and mouse counterparts and an equal distribution of conserved amino acids, suggesting that the proteins can fold into identical three-dimensional structures. The rat t-PA sequence contains two putative N-glycosylation sites at Asn-120 and Asn-452, while human t-PA has an additional glycosylation site at Asn-187. The site at Asn-187 is glycosylated in the human protein, revealing a different glycosylation pattern between the human and rat proteins.