Posttranslational modifications (PTMs) represent the main strategy Nature utilizes, in order to increase the proteome diversity beyond the limit posed by the 21 genetically encoded amino acids. PTMs result from the introduction of a specific functional group on a number of amino-acid side chains. The majority of PTMs are enzymatically introduced at the cellular level after ribosomal translation (e. g., phosphorylation, methylation, hydroxylation, glycosylation). However, there is another category of PTMs that does not require any enzymatic activity, being rather related to the intrinsic instability of proteins during their production and purification processes. Typical examples of such non-enzymatic PTMs are methionine and cysteine oxidation, pyroglutamate formation, deamidation of asparagine and the isomerization of aspartate. Occurrence of such chemical changes may significantly alter the structure and function of a given protein system.
In this project we work on the semisynthetic production of pharmaceutically relevant proteins (or protein domains) presenting deamidation/oxidation-related PTMs at ´´hot-spots´´ positions, namely those identified in the recombinant protein, with the long-term goal to characterize the structure and function of the chemically-modified variants and compare them with the native form.