Editing Protein quaternary structure (section)

==Protein–protein interactions==
{{main|Protein–protein interaction}}
Proteins are capable of forming very tight but also only transient complexes. For example, [[ribonuclease inhibitor]] binds to [[ribonuclease A]] with a roughly 20 fM [[dissociation constant]]. Other proteins have evolved to bind specifically to unusual moieties on another protein, e.g., biotin groups (avidin), phosphorylated tyrosines ([[SH2 domain]]s) or proline-rich segments ([[SH3 domain]]s). Protein–protein interactions can be engineered to favor certain oligomerization states.<ref>{{cite journal | vauthors = Ardejani MS, Chok XL, Foo CJ, Orner BP | title = Complete shift of ferritin oligomerization toward nanocage assembly via engineered protein-protein interactions | journal = Chemical Communications | volume = 49 | issue = 34 | pages = 3528–3530 | date = May 2013 | pmid = 23511498 | doi = 10.1039/C3CC40886H }}</ref>