Let’s gather ’round kids cause its story time once again. The story of… Proline (dun DUN DUUUUUNN!!!!!!!!)
There was once this amino acid named Proline. It looks like a common a.a , it’s cyclic and non-polar and has a fused ring structure (seems pretty normal right?) WRONG!! This amino acid is far from normal. The alpha carbon and the alpha amino group bond to form this ring structure, but this leaves no hydrogen free to be donated and to stabilize the structure of the alpha helix or a beta pleated sheet, thereby disrupting the structure!
The victims of proline’s wrath are said to be left horribly disfigured (a slight bend/kink in the structure due to the lack of the H-bond present.)
Legend has it that proline is still seen around bends, and lurking at the end of the structures, plotting it’s revenge….BOO!!