The figure below is a line and box model of a protein that is normally localized
ID: 167430 • Letter: T
Question
The figure below is a line and box model of a protein that is normally localized to the plasma membrane. Each box represents membrane spanning regions, while the arrow is showing where signal peptidase will act on the protein. Box one is located at the N-terminal end of the protein. Answer the following questions about this protein.
a. After signal peptidase function and transport to its ultimate localization, what side of the membrane will the N terminal portion of the protein be located on? What side will the C terminal portion of the protein be located on?
b. Suppose a mutation in the protein results in an amino acid change that prevents signal peptidase from recognizing the protein. How will the new protein be arranged in the membrane in its ultimate location?
Explanation / Answer
Q.No 1
Hydrophobic N-terminal signal sequence is mostly cleaved off by the signal peptidase. So the N-terminal portion of the protein will be located on the Endoplasmic Reticulum, mitochondria, or chloroplast and C-terminal will be located on the peroxisome.
Q.No 2
Due to mutation, the protein contains no specific target sequence. So the protein will be sent to cytosol.
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