The structure of aba is shown below. why was this a suitable substitution for a cys residue? under what circumstances would it not be suitable?

Answer and explanation;

-Aba is a suitable replacement because Aba and Cys have approximately the same sized side chain and are similarly hydrophobic.

-However, Aba cannot form disulfide bonds so it will not be a suitable replacement if these are required.

-Alpha-Aminobutyric acid is biosynthesized by transaminating oxobutyrate, a metabolite in isoleucine biosynthesis.