The 2 graphs below each show a hydrophobicity plot for a trans-membrane protein. Hydrophobicity plots are a bioinformatic tool that help predict whether a given protein has a hydrophobic region big enough to cross a membrane. It is based on a calculation of the free energy (AG) required to immerse each individual amino acid in water. The data are plotted as a running average of three consecutive amino acids, starting at the N terminal end Which of the following answer choices is correct concerning these two proteins. Protein 1 is on the left and protein 2 is on the right
Select one:
a. Protein 1 has 1 membrane spanning domain with the N-terminus facing the cytosol cross out
b. Protein 2 is a 4-pass integral membrane protein
c. Protein 1 is a 2-pass membrane spanning protein
d. Protein 2 is a 4-pass membrane spanning protein with the C-terminal domain in the cytoplasm
e. Protein 1 contains 1 alpha helical segment cross out cross out cross out cross out
The Correct Answer and Explanation is :
Based on the description of the hydrophobicity plots you provided, the correct answer to your question regarding the two proteins is likely:
d. Protein 2 is a 4-pass membrane spanning protein with the C-terminal domain in the cytoplasm
Explanation:
Hydrophobicity plots are used to predict transmembrane domains in proteins by identifying stretches of amino acids that are sufficiently hydrophobic to span the hydrophobic core of a lipid bilayer. These plots are typically generated by calculating the free energy change associated with moving each amino acid from a hydrophobic (membrane) environment to a hydrophilic (aqueous) environment. Peaks in the plot suggest potential transmembrane segments.
- Analysis of Protein 1:
- If the plot for Protein 1 shows fewer or less distinct peaks above the threshold typically required for spanning a membrane, it may indicate fewer transmembrane domains. Without the actual plot, we can’t conclusively determine if it has 1 or 2 passes, but we know it’s not as extensive as Protein 2.
- Analysis of Protein 2:
- If the plot for Protein 2 shows four distinct peaks that surpass the threshold for hydrophobicity, this would suggest that Protein 2 has four potential transmembrane domains. This makes it a 4-pass transmembrane protein.
- The orientation (N-terminus and C-terminus) can sometimes be inferred from the plot if there is a clear pattern of alternating hydrophilic and hydrophobic regions, indicating loops entering and exiting the cytoplasm and the extracellular space. If the plot suggests that the C-terminus ends on a hydrophilic note after the last hydrophobic peak, it likely remains in the cytoplasm.
Regarding the generation of the image from the URL you’ve shared, I’m not able to directly display or generate images from external URLs. However, I can create a similar hydrophobicity plot if you provide the amino acid sequence of the proteins or describe more about their characteristics. This way, we can visualize the properties as you described. Let me know if you would like to proceed with that or need help with another aspect of protein analysis!