Which of the following results provided evidence of a discrete nuclear localization signal somewhere on the nucleoplasmin protein? a. The nucleoplasmin protein was small and easily slipped through the nuclear pore complex. b. After cleavage of the nucleoplasmin protein, only the tail segments appeared in the nucleus. c. Removing the tail from the nucleoplasmin protein allowed the core segment to enter the nucleus. d. The SRP bound only to the tail of the nucleoplasmin protein, not the core segment.

Video transcript

Hi everyone. Let's look at our next question. What might happen if the nuclear localization signal is removed from a cargo protein. So let's think about what cargo proteins are and what a nuclear localization signal is. Well, cargo protein. Imagine taking cargo along is found on the vesicles that transport newly translated proteins where they're meant to go. And if they're meant to go to the nucleus, the cargo protein is labeled with the nuclear localization signal. And as we can guess, the name is a peptide fragment that serves as a signal that's recognized by proteins of the pathway into the nucleus. So the proteins that transport things into the nucleus. So the cargo protein attached to the bicycle which is transporting the protein has this peptide fragment called the nuclear localization signal that is recognized by those cells that are part of that transport system into the nucleus. So, if that signal is removed but will happen, that protein that was just synthesized and will no longer be recognized by the pathway into the nucleus. Well, the answer is it will just stay where it is, it will stay in the cytoplasm where it was synthesized. So, Choice C does say that the protein will stay in the cytoplasm. Nothing bad happens to it. It just can't get where it's supposed to go. It doesn't have that little label on it. So let's just look through our other answer choices. Choice A says the protein will be excreted from the cell. No, because there's no direction. They're telling it that it should be excreted. It'll just stay where it is because there's nothing uh there's no signal, there's no target, they're directing it anywhere else. So, Choice A is not correct. Choice B says the protein will enter the nucleus through different membranes. That's not correct. There is no different membrane. There's just the nuclear membrane and it needs that localization signal to interact with the pathway through the membrane. So Choice B. Is not correct. And then Choice D. Says the protein will be degraded. Well, there's no particular reason that protein will be degraded. That's not our answer. It just stays there in the cytoplasm. So what might happen if the nuclear localization signal is removed from a cargo protein? Choice? See, the protein will stay in the cytoplasm. See you in the next video.