About this Research Topic
Posttranslational modifications (PTMs) are key to any biological process. Commonly classified on the basis of the amino acid residue they target, PTMs are of two types: Ser, Thr, Tyr directed-Phosphorylation and Cys directed-S-oxidation, S-nitrosylation, S-palmitoylation and S-sulfhydration. Ample evidence has gathered over the years on their role in regulating cellular processes and their emerging role in regulating protein-protein interactions, protein-DNA interactions and structural regulation of protein. The emerging idea of crosstalk between PTMs where a modification of a particular site influences the modification at a site in its proximity or at a distance comprising of intra-modification (modification within the same class) or inter-modification (modification between the two classes) has only added more complexity to the already complex cellular system. Besides it has revealed the importance of PTM’s role in governing the system at the molecular level. Taken together, these findings make it necessary to study PTMs in detail.
Phosphorylation has served as the milestone among PTMs, being one of the first PTMs to be discovered, phosphorylation set the stage to the study of other PTMs and in terms of its detection western blot remained a sole technique. Methods making use of western blot were similarly devised to characterize the Cys-based PTMs. However, with western blot only a crude qualitative output can be achieved, and it is unreliable in identifying sites of modification and in making quantitative estimates where mass spectrometry has played a significant role. With the advent of mass spectrometry the information regarding PTMs has increased exponentially, in particular, the challenging task of relative quantitation (degree of modification between two sites) and absolute quantitation (proportion of modified versus unmodified site) has been made possible. This research topic invites original research papers and review articles which highlight the current progress made with respect to the strategies adopted to characterize PTMs by mass spectrometry especially methods involved in enriching modified protein or peptide, strategies utilized in quantitating PTMs, existing pitfalls relevant in quantitation strategies and new ways to counteract them.
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