Most protein domains exist as multiple variants with distinct structure and function

Abstract

BackgroundProtein domains are the active subunits that provide proteins with specific functions through precise three-dimensional structures. Such domains facilitate most protein functions, including molecular interactions and signal transduction. Currently, these protein domains are described and analyzed as invariable molecular building blocks with fixed functions. ResultsI show that most human protein domains exist as multiple distinct variants that I term "domain isotypes". Different domain isotypes are used in a cell, tissue, and disease-specific manner and have surprisingly different 3D structures. Accordingly, I find that domain isotypes, compared to each other, modulate or abolish the functionality of protein domains. ConclusionsMy results challenge the current view of protein domains as invariable building blocks and have significant implications for both wet- and dry-lab workflows. The extensive use of protein domain isotypes within protein isoforms adds to the growing body of evidence suggesting that the sciences should move from the current gene-centric research paradigm toward an isoform-centric research paradigm.