Linkers are naturally occurring short amino acid sequences that are used to separate domains within a protein. The advent ofrecombinant DNA technology has made it possible to combine two interacting partners by introducing artificial linkers thatoften, allow for the production of stable and functional proteins. Glycine-rich linkers are useful for transient interactions, espe-cially where the interaction is weak, by covalently linking proteins and forming a stable protein–protein complex. These linkershave also been used to generate covalently stable dimers and to connect two independent domains that create a ligand bindingsite or recognition sequence. Various structures of covalently linked protein complexes have been described using nuclear mag-netic resonance methods, cryo-electron microscopy techniques, and X-ray crystallography; in addition, several structures wherelinkers have been used to generate stable protein–protein complexes, improve protein solubility, and obtain protein dimers areinvestigated, and also the design and engineering of the linker in fusion proteins is discussed. Therefore, one of the main factorsfor linker design and optimization is their flexibility, which can directly contribute to the physical distance between the domainsof a fusion protein and describe the tendency of a linker to maintain a stable conformation during expression. We summarize theresearch on design and bioinformatics can be used to predict the spatial structure of the fusion protein. To perform simulationsof spatial structures and drug molecule design, future research will concentrate on various correlation models.
