ABSTRACT
Linkers and spacers are defined as IDRs of proteins that connect functional regions, whether they be ordered domains or disordered motifs. Their function is to provide appropriate spatial separation of the motifs, enable their spatially almost unrestricted
search for binding partners, and/or increase binding affinity by increasing local concentration, by virtue of the entropic gain from the physical connection of two binding elements, also known as the chelate effect (Jencks 1981). Another result is processivity, which results from alternative binding interactions of the two connected recognition elements with multiple binding sites along an elongated partner, without full release at any point. This binding capacity results in rapid diffusive movements along the substrate, as observed in the case of bacterial cellulase, matrix metalloproteinase 9 (MMP-9), and myosin VI (discussed in detail in Chapter 14, Section 14.9).
