Question

Biochemistry

"Thr-91 of Complex I is conserved through evolution. It is crucial for the functioning of Complex I in the Electron Transport Chain. I make two forms of mutant yeast: one in which Thr-91 is mutated to an alanine (Thr91Ala) and another in which Thr-91 is mutated to a tryptophan (Thr91Trp)."

Base on the data given, CREATE YOUR OWN QUESTION (best if can relates to electron transport chain of metabolism pathway). Then, find an ANSWER to your own question.

Answer 1

Which of the mutant will be more among themselves?

Threonine is a polar amino acid and can be phosphorylation due to the presence of -OH group. Since it is a polar amino acid so it can stabilize the tertiary structure by interacting with other polar amino acids present in its vicinity. Alanine is aliphatic amino acid due to the presence of -CH3 group. Mutation of Thr to Ala will drastically change the environment from hydrophilic to hydrophobic. As a result of it, the nearby residue will change their interacting partner and destabilize the tertiary structure. So, the activity of Complex I will reduce drastically.

Tryptophan is an aromatic amino acid which is bulkier than threonine and it requires more space as compared to threonine. Apart from that due to its hydrophobic nature it will not be able to fit in the space that was occupied by threonine. Also, it will break the tertiary structure of the protein as it will not be able to form a hydrophilic bond with the reside which are near to its vicinity. As a result of we will not any activity upon mutating Thr91 to Tpr.

So mutation of Thr to either alanine or Tpr will drastically change the activity of Complex I