What will most likely happen if one substitutes an amino aci

What will most likely happen if one substitutes an amino acid that is always absent from alpha helices, into a protein that is predominately alpha-helical? Disrupt secondary and tertiary structure; loss of function Maintain secondary structure but disrupt tertiary structure; maintain function Disrupt secondary structure but maintain the same tertiary structure; maintain function Disrupt secondary structure and gain in a novel function Ribosome will not synthesize it

Solution

Answer:

If one substitute an amino acid that is always absent from alpha helices, into a protein that is predominantly alpha-helical. Most likely, it would disrupt the secondary structure and tertiary structure and would eventually lead to the loss of function.

Explanation: Each amino acid has its alpha-helical propensity. Higher the propensity lower is the helical forming abilities. Proline (P) and Glycine (G) have high alpha-helical propensities (3.16 and 1.0 respectively) therefore, they are never found in the middle of an alpha-helix. In case if one inserts any one of this amino acid in the helix, the helix would distort or may end altogether. Disruption in the secondary structure of protein (alpha-helix is a sec. structure of a protein), would impact its further folding into the tertiary structure. The activity of the protein may lose if the helix has some role in the protein activity.