Question

Explain why treatment of a preparation of E. coli single strand binding protein (SSB) with acetic anhydride produces a chemically modified protein that is unable to bind to DNA.

[Hint: Acetic anhydride reacts with primary amino groups. Which amino acids would that include, and what would be the consequence of the reaction?]

3. Explain why treatment of a preparation of E. coli single strand binding protein (SSB) with acetic anhydride produces a chemically modified protein that is unable to bind to DNA. [Hint: Acetic anhydride reacts with primary amino groups. Which amino acids would that include, and what would be the consequence of the reaction?]

Answer 1

Acetic anhydride reacts with the primary Amino groups of the Amino acids like serine, threonine, lysine, cysteine, histidine and the aromatic Amino acid tyrosine. This reaction causes the formation of amide from the amine . When acetic anhydride treatment is given to E.coli SSB, amine groups of the proteins are converted to amide which causes the change in the structure of the protein. As such there is a change in the activity of the protein and SSB' s can no longer bind to the single strands of the DNA which hampers DNA replication and causes cell cycle arrest.