106:208663 Isolation and characterization of a cDNA encoding rat cationic trypsinogen. Fletcher, Thomas S.; Alhadeff, Myriam; Craik, Charles S.; Largman, Corey (Biochem. Res. Lab., Veterans Adm. Med. Cent., Martinez, CA 94553, USA). Biochemistry, 26(11), 3081-6 (English) 1987. CODEN: BICHAW. ISSN: 0006-2960. DOCUMENT TYPE: Journal CA Section: 3 (Biochemical Genetics) Section cross-reference(s): 7, 13 A cDNA encoding rat cationic trypsinogen [9002-08-8] was isolated by immunoscreening from a rat pancreas cDNA library. The protein encoded by this cDNA is highly basic and contains all of the structural features obsd. in trypsinogens. 9002-07-7 and 108007-29-0 are also in the experiment. The amino acid sequence of rat cationic trypsinogen is 75% and 77% homologous to the 2 anionic rat trypsinogens. The homol. of rat cationic trypsinogen to these anionic trypsinogens is lower than its homol. to other mammalian cationic trypsinogens, suggesting that anionic and cationic trypsins probably diverged prior to the divergence of rodents and ungulates. The most unusual feature of this trypsinogen is the presence of an activation peptide contg. 5 aspartic acid residues, in contrast to all other reported trypsinogen activation peptides which contain 4 acidic amino acid residues. Comparisons of cationic and anionic trypsins reveal that the majority of the charge changes occur in the C-terminal portion of the protein, which forms the substrate-binding site. Several regions of conserved charge differences between cationic and anionic trypsins have been identified in this region, which may influence the rate of hydrolysis of protein substrates.
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