When a Membrane Protein Is Radioactively Labeled During Synthesis and Followed

Multiple Choice

When a membrane protein is radioactively labeled during synthesis and followed through the various organelles in the secretory pathway,all the radioactivity is concentrated in the cis-Golgi apparatus six hours after the protein synthesis.This suggests that the protein

A) was imported directly into the cis-Golgi posttranslationally.
B) contains a KDEL sequence near its C-terminus.
C) has a membrane-spanning domain length equals the thickness of the cis-Golgi membrane.
D) has a mannose-6-phosphate tag.
E) is misfolded and being degraded in the cis-Golgi.