A leader or secretory signal sequence acts as a peptide signal bound by cellular machinery early in the translation process. This allows for the correct localization of the translation complex to the endoplasmic reticulum where the antibody chains can enter into the secretory pathway for protein assembly and secretion from the cell. The leader sequence is cleaved during the protein assembly process and is not a part of the final protein. Twist recommends the following leader sequence for both heavy and light chains when using our pTwist IgG expression vectors as these sequences have been tested and validated with our pTwist vectors in both Expi293™ and ExpiCHO™ cell lines:

VH: MRAWIFFLLCLAGRALA

VL: MRAWIFFLLCLAGRALA