aamc test 2 spoilers help with graph question

[giguerex35]

Can someone please explain why this is the correct answer beyond what the rationale says. Please be as thorough as possible. Thanks

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[aldol16]

The Y229A mutation doesn't do anything to protein activity (Figure 2 caption) but it shifts the melting point of the protein to lower melting points. Since mutating it away makes the protein melt easier, its presence must be stabilizing the protein in some way.

 

[Lawpy]

So Figures 2 and 3 are needed to answer the question. Figure 2 caption says the Y229A mutation shows the same activation as wild type, which means Y229A mutation doesn't affect cAMP activation. As such, Y229 is not critical for cAMP activation. Figure 3 shows a leftward curve shift for the Y229A thermal denaturation profile. This means more of the Y229A mutant protein is unfolded/denatured at lower temperature (look at the axes of Figure 3 chart). So Y229A mutation lowers the stability of the protein, which implies Y229 is necessary for protein stability.

 

[giguerex35]

So Figures 2 and 3 are needed to answer the question. Figure 2 caption says the Y229A mutation shows the same activation as wild type, which means Y229A mutation doesn't affect cAMP activation. As such, Y229 is not critical for cAMP activation. Figure 3 shows a leftward curve shift for the Y229A thermal denaturation profile. This means more of the Y229A mutant protein is unfolded/denatured at lower temperature (look at the axes of Figure 3 chart). So Y229A mutation lowers the stability of the protein, which implies Y229 is necessary for protein stability.

The Y229A mutation doesn't do anything to protein activity (Figure 2 caption) but it shifts the melting point of the protein to lower melting points. Since mutating it away makes the protein melt easier, its presence must be stabilizing the protein in some way.

Much appreciated thanks