Post-translational modifications increase the complexity of the proteome compared to the genome. Such modifications serve to expand the chemical functionality of natural proteins.  These modifications serve many important roles in a wide variety of biochemical processes. As such, overwhelming research efforts have focused on identifying the type and location of these post-translational modifications. The biochemical functional consequences of post-translational modifications have also been studied to some extent. In comparison, there have only been limited studies on the effect of post-translational modifications on structural stability. Since the secondary structures alpha-helix and beta-sheets are the basic three dimensional building blocks for protein structures, we have investigated the effect of various post-translational modifications on secondary structure stability. Modifications including Ser/Thr phosphorylation and glycosylation, Asn glycosylation, Arg methylation and deimination, and Lys methylation and acetylation were investigated. Alanine-based peptides were used to explore the effect of post-translational modifications on helix N-capping, C-capping, and propagation (propensity). All peptides were synthesized by solid phase peptide synthesis using Fmoc-based chemistry. The peptides were investigated by circular dichroism spectroscopy coupled with modified Lifson-Roig theory. Two series of hairpin (strand-turn-strand) forming peptides were used to explore the effect of post-translational modifications on sheet forming energetics. Complete sequence specific assignment for the peptides was achieved using 2D 1H NMR TOCSY, DQF-COSY, and ROESY spectra. The Ha chemical shifts were used to derive the folding energetics. These studies should complement functional studies on post-translational modifications and provide the foundation for predicting the effect of post-translational modification on protein structure stability.

Effect of post-translational modifications on secondary structure stability

248th National Meeting (2014)

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