Editing Protein quaternary structure (section)

== Role in Cell Signaling ==
Protein quaternary structure also plays an important role in certain cell signaling pathways. The G-protein coupled receptor pathway involves a heterotrimeric protein known as a G-protein. G-proteins contain three distinct subunits known as the G-alpha, G-beta, and G-gamma subunits. When the G-protein is activated, it binds to the G-protein coupled receptor protein and the cell signaling pathway is initiated. Another example is the receptor tyrosine kinase (RTK) pathway, which is initiated by the dimerization of two receptor tyrosine kinase monomers. When the dimer is formed, the two kinases can phosphorylate each other and initiate a cell signaling pathway.<ref>{{cite journal | vauthors = Heldin CH | title = Dimerization of cell surface receptors in signal transduction | journal = Cell | volume = 80 | issue = 2 | pages = 213–223 | date = January 1995 | pmid = 7834741 | doi = 10.1016/0092-8674(95)90404-2 | s2cid = 18925209 | doi-access = free }}</ref>