1. Which of the following experiments can be used to demonstrate that a nuclear
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Question
1. Which of the following experiments can be used to demonstrate that a nuclear localization signal (NLS) is sufficient for nuclear transport of proteins?
A. Express a cytosolic protein fused to a NLS and observe its localization by immunofluorescence
B. Express a GFP tagged mitochondrial protein and observe its localization by immunofluorescence
C. Express a GFP tagged nuclear protein and observe its localization by immunofluorescence
D. Express a nuclear protein that does not have a NLS, and observe its localization by immunofluorescence
2. Which of the following is NOT true of nuclear import/export
a. Imported proteins must interact with RanGTP in the cytosol
b. Importins release their cargo upon interacting with RanGTP
c. Proteins destined to the nucleus must have a nuclear localization signal
B. Express a GFP tagged mitochondrial protein and observe its localization by immunofluorescence
C. Express a GFP tagged nuclear protein and observe its localization by immunofluorescence
D. Express a nuclear protein that does not have a NLS, and observe its localization by immunofluorescence
2. Which of the following is NOT true of nuclear import/export
a. Imported proteins must interact with RanGTP in the cytosol
b. Importins release their cargo upon interacting with RanGTP
c. Proteins destined to the nucleus must have a nuclear localization signal
Explanation / Answer
1.
The correct answer is option (C).
Express a GFP tagged nuclear protein and observe its localization by immunofluorescence
The protein, which is imported to the nucleus from the cytosol consists of a signal known as the nuclear localization signal (NLS) that are bound by the importin. This sequence hgas a tag. The importins and exportins are involved in the transport of the cargo regualted by the Ras GTPase and Ran. A specialized mRNA protein moves it to the cytoplasm after the post transcriptional modification. This is acheived by the Ran protein. The genes that are transcribed are located near the nuclear pores that facilitate the translocation. Hence, a GFP can be tagged to a nuclear protein and observe its localization by immunofluorescence.
2.
The correct answer is option (A).
a. Imported proteins must interact with RanGTP in the cytosol
The protein, which is imported to the nucleus from the cytosol consists of a signal known as the nuclear localization signal (NLS) that are bound by the importin. This sequence hgas a tag. The importins and exportins are involved in the transport of the cargo regualted by the Ras GTPase and Ran. GTPases hydrolyze to release the energy. The GTP hydrolysis occurs in the cytosol that releases Ran from the importin. Once the protein are inside the nucleus their interaction with Ran-GTP cause a conformational change in the importin to release their cargo.
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