Question

The diagram below represents a hypothetical enzyme protein with 100 amino acids. The number scale indicates the position of each amino acid. This enzyme is regulated by an allosteric inhibitor.

Amino Acid position number

0         10           20         30         40         50         60         70         80         90        100

I______I_______I______I______I______I______I______I______I______I______I

                          I<------------------>I                                    I<--------->I                                         

                                Active Site                                       Allosteric Site

1. What would be the likely effect on this enzyme’s activity if there were three separate point deletion mutations in the codons for the amino acids between position 4 and 12? Justify your answer with a brief description.
2. What would be the likely effect on this enzyme’s activity if there was a point insertion mutation in the codon for the amino acid at position 37? Justify your answer with a brief description
3. What would be the likely effect on this enzyme’s activity if there was a substitution mutation in the third base in the codon for the amino acid at position 50? Justify your answer with a brief description.

Answer 1

a)

Three separate point deletion mutations in the codons between positions 4 and 12 would likely have no to very little effect on the function of the enzyme. This is because the occurrence of three separate point deletions would not affect the frame of the protein and since amino acids 4 to 12 are not in the active site nor in the allosteric region, this mutation would likely have very little effect on the activity of the enzyme.

b)

If there were a point insertion mutation in the codon for the amino acid at position 37, the protein would likely become non-functional. This is because position 37 is within the active site of the protein, and an insertion mutation at this site would cause the active site to become non-functional.

c)

A substitution mutation of the third base of the 50th codon would likely have no effect on protein function. This is because of two primary reasons:

1) The third base of a codon can often be mutated to another base without it affecting the amino acid sequence due to third base wobble.
2) Amino acid 50 is not involved in either the active site nor is it a part of the allosteric regulator binding of the protein, therefore a mutation of this codon is unlineky to impact fnction.