The Ramachandran Plot was described on 1963 by Ramachandran, G.N.; Ramakrishnan, C.; Sasisekharan, V. [1]
Ramachandran outliers are those amino acids with non favorable dihedral angles, and Ramachandran plot is a powerful tool for making those evident. Most of the times, Ramachandran outliers are a consequence of mistakes during the data processing.
However, sometimes, Ramachandran outliers might play a special role in the structure function. See for example the case of Ser-200 in the structure . Let's draw its .
Notice that the residues in are colored in yellow, the residues in colored in magenta, in blue and in white. At any time you may residues.
Only Gly are allowed in the lower right-hand side quarter. If we from the plot, will find the , with angle values considered non favourable for a Serine .
However, in this case a misplaced residue (Ser 200) seems to play an important role in the function of this structure, leading to the alpha/beta fold (Ollis et al, 1992)
