The typo does not affect the answer so I would not dwell on their mistake. The key thing was to determine what happens to the protein in the sequence of events described in the passage. I know these kinds of mistakes can be annoying but the reasoning of the Q and answer is not really affected by the typo. I agree with above you should reach out to the AAMC and let them know about their boo boo. I'm sure they'll reply with some technicality about how the term is not wrong per se, but just an odd choice etc... but that's just the AAMC 🙂
Good luck!