*2.2. Marshalling a Diverse Set of Responding Proteins More or Less in Unison*

When combined with the concept of the role of intrinsic disorder in signalling, the significance of epiproteomic changes are placed in a new light. Coherently controlled epiproteomic changes would have the potential to alter the response of many proteins simultaneously, whether they be members of the same protein complex or dispersed complexes that need to be coordinated with each other. Individual PTM changes have been shown to play key roles in a number of different properties including the formation or dissolution of protein interactions [12], the conformation of a protein [13], the membrane localisation of a protein [14] or the inactivation [15] or degradation [16] of a protein. When such changes are driven by a significant change in physiology of the entire cell, such as its redox potential or pH, there is significant scope for matching coordinated changes in the protein complexes within the cell that need to react to the new state. Thus, the epiproteome is uniquely positioned to play a vital role in marshalling multi-protein responses. There are some known examples of this in situations of stress in nature already. A plant pathogen effector was recently shown to acetylate several proteins that interact with each other in a complex [17]. Another example is the cell signalling that results from electrophilic oxidized lipid products, so called reactive lipid species (RLS), that can react with the amino acids cysteine, lysine and histidine because of their nucleophilic nature. RLS effects on signalling events are largely restricted to the modification of cysteine residues in proteins. RLS induced modifications appear to participate in multiple physiological processes including inflammation, induction of antioxidants and even cell death through the modification of signalling proteins [18].
