You have identified a protein pair, named Alpha 1 and Zeta1, which bind to each other to form a heterodyne. You made two mutants in these proteins. The first is designated alpha1 and carries a Lys to Asp change in the amino acid sequence. The second, designated zeta1 carries a Glue to Lys change in the amino acid sequence. You test to see if different combinations of Alpha 1 and Zeta1 pairs will bind to each other, and the results are summarized in the following table: For the mutant alpha1-, the amino acid change caused a difference in binding to Zeta1. You have found another mutant, alpha1^+, whose same Lys has also changed into another amino acid. However, these mutants bind to Zeta1 the same as the Alpha1 wild-type. Please predict one possible amino acid changes in alpha1^+ that would give this result and explain your reasoning. Similarly, you have found a mutant, zeta1^+, that binds to Alpha 1 the same as the Zeta1 wild-type. Please predict one possible amino acid changes in zeta1^+(of the same Glu) that would give this result and explain your reasoning.
1. Wildtype Alpha1 and Zeta1 can bind to each other by means of ionic interaction made between positively charged aminoacid Lysine and Negatively charged aminoacid Glutamic acid (Glu).
2. Mutant Alpha1- can bind with mutant zeta1- because in alpha1- , lysine is replaced by Asp (Aspartic acid) which is a negatively charged aminoacid and in zeta1-, glutamic acid is replaced by Lysine which is a positively charged aminoacid. So the ionic interaction is possible for binding.
D. In alpha1+, Lysine (Lys) might have changed into Arginine (Arg) which is also a positively charged aminoacid. So alpha1+ with Arginine (+) can bind with Glutamic acid (-) in Zeta1 (wildtype).
E. In Zeta1+, Glutamic acid (Glu) might have changed to Aspartic acid (Asp) which is also a negatively charged amino acid. So Zeta1+ with Aspartic acid (-) can bind with lysine (+) in Alpha1 (wildtype)
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