Customized expression of recombinant proteins can also accelerate scientific discovery. From functional assays to structural research, recombinant proteins are extremely valuable tools for the scientific community. The data below from Yao G et al. illustrates in an elegant way how to use custom made recombinant proteins.

Figure 3. Botulinum toxin (Botox) is a large protein that is composed of three domains (upper right corner, crystal structure shown in yellow, green, and pink). A recent study reveals a novel mechanism by which the toxin hijacks three receptors on the host neuronal surface as its "GPS" - the peptide moiety of protein SV2 (green-blue ribbon model), a conserved glycan modification of SV2 (green and light blue sticks), and a lipid (brown sticks) - to launch its attack. Credit: Rongsheng Jin and Guorui Yao / UCI.
Note: Recombinant glycosylated SV2 isoform C was custom made by BioLegend; expressed in, and secreted from HEK 293 cells. Nat Struct Mol Biol. 2016 Jul; 23(7): 656–662, Pubmed.