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Rat pancreatic kallikrein mRNA: nucleotide sequence and amino acid sequence of the encoded preproenzyme
Abstract:
We have cloned via recombinant DNA technology the mRNA sequence for rat pancreatic preprokallikrein. Four cloned overlapping double-stranded cDNAs gave a continuous mRNA sequence of 867 nucleotides beginning within the 5'-noncoding region and extending to the poly(A) tail. The mRNA sequence reveals that pancreatic kallikrein is synthesized as a prezymogen of 265 amino acids, including a proposed secretory prepeptide of 17 amino acids and a proposed activation peptide of 11 amino acids. The activation peptide, although similar in length, is distinct from those of the other classes of pancreatic serine proteases. The amino acid sequence of the predicted active form of the enzyme is closely related to the partial sequences obtained for other kallikrein-like serine proteases including rat submaxillary gland kallikrein, pig pancreatic and submaxillary gland kallikreins, the gamma subunit of mouse nerve growth factor, and rat tonin. Key amino acid residues thought to be involved in the substrate-cleavage specificity of kallikreins are retained. Hybridization analysis showed relatively high levels of kallikrein mRNA in the rat pancreas, submaxillary and parotid glands, spleen, and kidney, indicating the active synthesis of kallikrein in these tissues.
Insights
Researchers cloned the rat pancreatic preprokallikrein mRNA sequence, revealing its synthesis as a prezymogen. This enzyme shows close relation to other kallikrein-like proteases and is actively synthesized in multiple rat tissues.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Kallikreins are serine proteases involved in various physiological processes.
- Understanding the structure and synthesis of pancreatic kallikrein is crucial for its functional studies.
Purpose of the Study:
- To clone and characterize the mRNA sequence of rat pancreatic preprokallikrein.
- To elucidate the amino acid sequence and potential functional domains of the enzyme.
Main Methods:
- Recombinant DNA technology was used to clone overlapping double-stranded complementary DNAs (cDNAs).
- Nucleotide sequencing determined the continuous mRNA sequence.
- Hybridization analysis assessed mRNA levels in various rat tissues.
Main Results:
- A continuous mRNA sequence of 867 nucleotides for rat pancreatic preprokallikrein was obtained.
- The enzyme is synthesized as a 265-amino acid prezymogen with distinct prepeptide and activation peptides.
- The predicted active enzyme sequence is homologous to other kallikrein-like proteases, retaining key residues for substrate specificity.
- High kallikrein mRNA levels were detected in the pancreas, salivary glands, spleen, and kidney.
Conclusions:
- The study provides the complete mRNA sequence for rat pancreatic preprokallikrein.
- The findings reveal structural insights into the enzyme's synthesis and its relationship to other kallikreins.
- Active synthesis of kallikrein in multiple tissues suggests diverse physiological roles.