Editing Protein structure (section)

===Structural domain===
A [[structural domain]] is an element of the protein's overall structure that is self-stabilizing and often [[protein folding|folds]] independently of the rest of the protein chain. Many domains are not unique to the protein products of one [[gene]] or one [[gene family]] but instead appear in a variety of proteins. Domains often are named and singled out because they figure prominently in the biological function of the protein they belong to; for example, the "[[calcium]]-binding domain of [[calmodulin]]". Because they are independently stable, domains can be "swapped" by [[genetic engineering]] between one protein and another to make [[chimera (protein)|chimera]] proteins. A conservative combination of several domains that occur in different proteins, such as [[protein tyrosine phosphatase]] domain and [[C2 domain]] pair, was called "a superdomain" that may evolve as a single unit.<ref>{{cite journal | vauthors = Haynie DT, Xue B | title = Superdomains in the protein structure hierarchy: The case of PTP-C2 | journal = Protein Science | volume = 24 | issue = 5 | pages = 874–882 | date = May 2015 | pmid = 25694109 | pmc = 4420535 | doi = 10.1002/pro.2664 }}</ref>