Question

What two things could be effected in the secondary structure if tryptophan was substituted for glycine?

Answer 1

1) Glycine is an amino acid having two hydrogen atom on the C- carbon which allows it to have highest flexibility among the amino acids thus have very much less tendency to form alpha helix structure. Whereas if there is tryptophan instead of glycine it will have certain conformation due to its phenolic group, present at the C- position. Thus will have a grater tendency to be found in the alpha helices than the glycine.

2) Glycine have the lowest propensity factor for the alpha helices whereas tryptophan has a way greater propensity factor for tryptophan, thus also found in alpha helices. Glycine is generally found in the beta turn kind of secondary structure, thus if glycine is substituted by tryptophan the beta turn secondary structure will also loose their activity as well as stability also.