localiastion in the 6. You are studying a cargo protein which you believe is inv
ID: 261024 • Letter: L
Question
localiastion in the 6. You are studying a cargo protein which you believe is involved in nuclear transport. You have created various truncation mutations in the cargo protein in which certain portions of are removed You determine whether the cargo protein localizes to the nucleus and/or cytoplasm under normal conditions and also in the presence of leptomycin B, an inhibitor of the nuclear export machinery Your data are shown in the following figure. (A plus means the cargo protein is located in that part of the cell, a minus that it isn't.) ptomycin B acids nucleus yloplasm nucles cytopls 1-750 + 151-750 + 451-750 01-450 51-450+ 1-150 151-300 A. (4pts) Why does the removal of parts of this cargo protein (and others) cause the cargo protein to change its location in the cell? B. (4pts) How can you use this information to determine the location of a nuclear localization sequence (NLS) in this cargo protein? C. (2pts) What range of amino acids do you think contains the NLS? D. (2pts) What range of amino acids do you think contains the NES?Explanation / Answer
Proteins imported to or exported from the nucleus through nuclear pores contain a specific amino acid sequence that fuctions as a Nuclear localization signal (NLS) or a nuclear export signal. NLS directs nuclear proteins to the nucleus whereas nuclear export signal transports the protein to the cytoplasm.
a) If NLS sequence is removed then the transport of the cargo protein to the nucleus will be inhibited and thus it will remain in the cytolpasm. Likewise, If nuclear export signal sequence is removed the transport of cargo protein to the cytoplasm will be inhibited and the cargo protein will remain in the nucleus.
The sequence removed in the cargo protein is either NLS or nuclear export signal, resulting in the cargo protein to remain in cytoplasm or nucleus, respectively. When both signals are present, the protein localization is both cytoplasm and nucleus (as shown in the chart.)
b) By compairing the amino acid sequence deletion or presence and resulting protein localization can determine the locatopn of NLS in the cargo protein
c) The transport to nucleus was inhibited on removing the amino acids from 301 to 450 but when only this sequence 301 to 450 was present the cargo protein was present in nucleus and absent in cytoplasm. This clearly indicates that sequence 301 to 450 is nuclear localization signal sequence that directs the cargo protein from cytoplasm to nucleus.
d) On removing amino acids from position 151-300 the cargo protein remain in the nucleus, indicates the transport of protein to cytoplasm is inhibited. But when only 151-300 positioned amino acid were present, the cargo protein is transported to cytoplasm and was absent in the nucleus. This transport clearly indicates the sequence 151-300 is the nuclear export signal sequence that directs the transport of protein to the cytoplasm.
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