You are studying a protein that you call Protein X. There is an aspartic acid at a key position in Protein X that is important in the folding and stabilization of that protein. If this aspartic acid is changed to a different amino acid, which one of the following amino acid substitutions is MOST likely to allow the protein to fold normally?

threonine

arginine

serine

glycine

glutamic acid

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Irving HeathcoteLv2

29 Sep 2019

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1.You are studying the worldâs smallest enzyme which has the amino acid sequence of:

Met Ala Ser Met Tyr Ala Glu

You know that activity of this enzyme requires phosphorylation. You wish to design an inactive mutant form of this enzyme that can never be phosphorylated. You will use site-directed mutagenesis to alter the DNA sequence of this protein, resulting in a mutant protein.

Additional information: The most common resides to be phosphorylates are serine, threonine and tyrosine. In theory, these can be replaced with any other amino acid except for glutamic and aspartic acid, the shape and charge of a phosphorylated serine and aspartic acid are similar. Substitution with one of these amino acids would create a protein that looked like it was always phosphorylated (phosphomimic). Alanine is one of the most common substitutions, but others are possible and sometimes preferable to preserve other characteristics of the amino acid.

1. Write out the resulting amino acid sequence corresponding to your designed mutant protein here:

Assuming that the mutations are adaptive, how would that affect the stability of a protein at low and high temperatures?

Given:

1) Glutamine to lysine in a warm adapted species.Glutamine is uncharged while lysine is positively charged, therefore there would likely be a change as an uncharged amino acid is being replaced with positively charged amino acid.

2) Threonine to Alanine in a warm adapted species. Threonine is polar uncharged while Alanine is hydrophobictherefore there would likely be a change, as a polar charged amino acid is being replaced with a hydrophobic amino acid.

3) Glutamic acid to aspartic acid in a cold adapted species. Both Aspartic acid to Glutamic acid are negatively charged, therefore, there would likely be no effect with this change as both are negatively charged amino acids.

4) Glycine to alanine in a warm adapted species. Both Glycine to Alanine are non polar amino acids, therefore the change would likely have no effect as both are non polar and hydrophobic.