A protein DHFR is coupled to a mitochondrial signal sequence and expressed in a mammalian cell to assess protein trafficking to different organelles. DHFR is stimulated to fold when the small molecule X is added to cells. A scientist incubates cells expressing DHFR with X, and then fractionates cells to see where DHFR is located. He will find that he will recover DHFR from:_____.
a. the nucleus.
b. mitochondria.
c. the cytosol.
d. the ER.
e. peroxisomes.