The major difference is the fact that it has a hydrophobic signal sequence.
This cartoon shows that this is the first part of the protein produced.
After the signal sequence is completed, protein synthesis is further
inhibited. This is to allow the interaction of the signal sequence
with a complex
on the rough endoplasmic reticulum. In the above cartoon, note
that the signal peptide is allowed to enter and essentially guide the protein
into the
lumen of the rough endoplasmic reticulum. Once the signal sequence
is detected, protein synthesis resumes and the rest of the protein is inserted
in
the lumen. Note that a signal peptidase near the inner surface
of the membrane works to cleave the signal sequence from the growing peptide.