Your lab assistant put together DNA sequences to create a modified polypeptide sequence, then exp…
your lab assistant put together DNA sequences to create a
modified polypeptide sequence, then expressed these constructs in
some brain cells. For each of the following constructs, predict the
intracellular (or extracellular) location, and a brief description
of why. Assume a start codon is present.
a) a protein normally targetted to the chloroplast stroma, with
N-terminal targeting sequence deleted.
b) a C-terminal peroxisomal targeting sequence has been asses to
the C-terminus of a normally secreted protein, still with its usual
N-terminal signal sequence.
c) the addition of an N-terminal mitochondrial targeting
sequence to a protein with internal nuclear localization
d) moving the N-terminal signal sequence of a secreted protein
to the C-terminus of the protein.
I am very lost so please explain in some detail and/or if you
know any videos or websites on these concepts I would be very
a. if the N-terminal targeting
sequence is deleted, the protein will no more be recognized to be
targeted to the chloroplast stroma. It will not go to chloroplast
stroma. It will also not be secreted extracellularly. It may get
stuck in the cytoplasm or chloroplast membrane.
b. the protein will still be
recognized for secretion because its N-terminal signal sequence is
intact. The peroxisomal target sequence is after the protein
sequence which will not be prioritized by the cell.
c. the protein will now be localized
to the mitochondria
d. it will remain intracellularly
now, and won’t be secreted out of the cell