Sequence Analysis of the Carboxypeptidase E Precursor
With the use of recombinant DNA technology, much has recently been learned about precursors of proteins and bioactive peptides. Sequencing of cDNA clones has revealed that many proteins are originally produced as larger precursors. These protein precursors must be post-translationally processed into the active protein. One of the best studied precursor sequences is the ‘signal peptide’, which is typically a hydrophobic 20–25 amino acid peptide located on the N-terminus of the protein precursor (Von Heijne, 1985). The signal peptide is usually removed by a signal peptidase located in the endoplasmic reticulum. Most proteins that are secreted or localized to subcellular organelles initially contain signal peptides, which directs the translocation of newly synthesized proteins into the rough endoplasmic reticulum. In addition to signal peptides, many proteins contain other precursor sequences. Examples of proteins that are produced from larger precursors (containing more than a signal peptide) include receptors, such as the insulin receptor (Ebina et al, 1985), enzymes, such as carboxypeptidase A (Quinto et al, 1982) and prothrombin (Degen et al, 1983), and numerous peptide hormones and neurotransmitters (Docherty and Steiner, 1982).
KeywordsSignal Peptide Secretory Granule Basic Amino Acid Chromaffin Granule Signal Peptide Cleavage Site
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