Why does the template for EasyXpress Disulfide Insect Kits need to have a signal sequence (such as the mellitin signal sequence as provided by the EasyXpress Linear Template Fab Kit primers)?

The signal sequence ensures that the expressed protein is quantitatively translocated into the vesicles contained in the lysate. These vesicles represent a distinct compartment derived from the endoplasmic reticulum (ER); they contain the enzymes and chaperones from the ER which are responsible for correct folding and posttranslational modifications such as disulfide bond formation and glycosylation.