Human interleukin 2 signal peptide
N-terminal secretory signal peptide of human interleukin 2 (IL-2). Placed at the N-terminus of a protein, it directs the protein into the endoplasmic reticulum for secretion, and signal peptidase then removes it. Used to secrete cytokines, growth factors, and secreted reporters from mammalian cells.
Origin: Human interleukin 2 precursor
Characteristics
The cloned IL-2 cDNA encodes a 153-residue precursor whose hydrophobic N-terminal 20 residues, Met-Tyr-Arg-Met-Gln-Leu-Leu-Ser-Cys-Ile-Ala-Leu-Ser-Leu-Ala-Leu-Val-Thr-Asn-Ser, act as the secretory signal. Signal peptidase cleaves between Ser at position 20 and Ala at position 21, leaving a mature IL-2 of 133 amino acids with a calculated molecular weight of 15,420.5, close to the 15,000 measured for IL-2 purified from Jurkat cells. The sequence stored here covers residues 2-20: the initiator ATG is omitted, and the 3' end carries an EcoRI site introduced by silent codon changes (ACA to ACG, AAC to AAT, AGT to TCG) that leave the encoded peptide unchanged.
Applications: N-terminal secretion signal for cytokines, growth factors, and secreted reporters expressed from plasmid or viral vectors in mammalian cells. Native signal for secretion of IL-2 itself, as in the original cDNA expression in COS cells.
Limitations: The stored sequence has no initiator ATG, so a start codon must come from the vector or from an upstream fusion partner; it is not translatable on its own. Its 3' EcoRI site is a cloning junction rather than IL-2 sequence, so the fragment is 57 nucleotides where the full 20-residue signal is 60. Cleavage efficiency depends on the downstream cargo.
Sequence
References
- Taniguchi et al. (1983). Structure and expression of a cloned cDNA for human interleukin-2. Nature - Taniguchi 1983 IL-2 cDNA
- von Heijne et al. (1990). The signal peptide. J Membr Biol - vonHeijne 1990 Signal Peptides