SERINE PHOSPHORYLATION EFFECT ON SECONDARY STRUCTURE PREDICTION OF INTRINSICALLY UNSTRUCTURED AND ORDERED STRUCTURED PENTAPEPTIDES BY RAMACHANDRAN ANALYSIS

Many proteins associated with cell signalling pathways are often targets of post-translational modifications such as phosphorylation, glycosylation, ubiquitination, nitrosylation, methylation, acetylation, lipidation and proteolysis. Such modifications can lead to the induction or disruption of secondary structural elements of the modified protein. This paper describes the structural behaviour of a set of intrinsically disordered peptides (IDP) and ordered structured peptides (OP) modified by phosphorylation on a serine residue. These pentapeptides (IDP and OP) derived from fragmentation of proteins from different organisms. Ramachandran analysis revealed that both, IDP and OP, have an overall propensity for α-helical structure that is greatest in IDP and non-existent in OP cluster conformations. Phosphorylation of OP caused a decrease in the helical propensity in the serine phosphorylated residues, whereas for IDP with high disorder tendency, the opposite was observed and phosphorylation engendered alpha left-handed helical propensity.