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.

Verified step by step guidance

1. Step 1: Understand the question. The question is asking which of the given options provides evidence that there is a discrete nuclear localization signal (NLS) on the nucleoplasmin protein. The NLS is a specific sequence of amino acids that directs a protein to the nucleus.
2. Step 2: Review each option carefully. Option a suggests that the nucleoplasmin protein is small and can easily pass through the nuclear pore complex. This doesn't provide evidence of a NLS because size alone doesn't determine whether a protein can enter the nucleus.
3. Step 3: Consider option b. This option states that after cleavage of the nucleoplasmin protein, only the tail segments appeared in the nucleus. This suggests that the tail segments contain the NLS, as they are the only parts that enter the nucleus.
4. Step 4: Look at option c. This option suggests that removing the tail from the nucleoplasmin protein allows the core segment to enter the nucleus. This doesn't provide evidence of a NLS because it suggests that the tail was preventing the core from entering the nucleus, not that the core has a NLS.
5. Step 5: Finally, consider option d. This option states that the SRP (signal recognition particle) only binds to the tail of the nucleoplasmin protein, not the core segment. This doesn't provide evidence of a NLS because the SRP is involved in targeting proteins to the endoplasmic reticulum, not the nucleus. Therefore, the correct answer is option b.