Answer:
N-terminal signal sequence --> STS --> internal signal sequence --> STS --> internal signal sequence --> STS
Step-by-step explanation:
Steroid Sulfatase (STS) is a signal localized in the endoplasmic reticulum, it catalyzes the desulfation reaction
N-Terminal is the protein domain that is outside of the cell membrane
The internal signal sequence directs the protein to the membrane of the endoplasmic reticulum, this signal is also responsible for open the membrane pore