Question

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.

Answer 1

Charged amino acids such as positively and negatively, frequently form salt bridges. These interactions are important for the stabilization of the three-dimensional structure of protein. For instance, proteins of thermophilic organisms which are in habitant at elevated temperatures and survives at extreme temperatures? 80-90 °C, they often possess extensive network of salt bridges on their protein surface provides thermostability to these proteins, prevent them from denaturation due to existing high temperatures of the environment. Similarly, increase in the hydrophobic strength of the protein also provides thermos-stability to protein. Therefore, based on this we can assume following.

1. Glutamine to lysine cause change in neural to positively charged acid resulting increase in the salt bridges causing increase in the thermotolerance against high temperature.

2. Change from threonine to alanine i.e., polar to hydrophobic amino acid, which will increase the hydrophobicity of protein and increases hydrophobic strength and make them stable against warm environment.

3. Aspartic acid to Glutamic acid are negatively charged polar amino acid and enhances the interaction of protein to the water surface, and reduces the hydrophobic core strength which are susceptible for frost bite.

4. Both glycine and alanine are non-hydrophobic amino acids which provides stretch to the hydrophobic core of the protein. Therefore, change from the Glycine to alanine will not affect the stability of protein.