Editing Expression vector (section)

===Protein tags===
{{main|Protein tag}}
After the expression of the gene product, it may be necessary to purify the expressed protein; however, separating the protein of interest from the great majority of proteins of the host cell can be a protracted process. To make this purification process easier, a [[Protein tag|purification tag]] may be added to the cloned gene. This tag could be [[Polyhistidine-tag|histidine (His) tag]], other marker peptides, or a [[fusion protein|fusion partners]] such as [[glutathione S-transferase]] or [[maltose-binding protein]].<ref>{{cite journal |title= Overview of Affinity Tags for Protein Purification |author1=Michelle E. Kimple |author2=Allison L. Brill |author3=Renee L. Pasker |journal=Current Protocols in Protein Science |date=24 September 2013 | volume=73|issue=Unit-9.9 |pages=9.9.1–9.9.23 |pmid= 24510596 |pmc=4527311 |doi= 10.1002/0471140864.ps0909s73 |isbn=978-0-471-14086-3 }}</ref> Some of these fusion partners may also help to increase the solubility of some expressed proteins. Other fusion proteins such as [[green fluorescent protein]] may act as a [[reporter gene]] for the identification of successful cloned genes, or they may be used to study protein expression in [[Live cell imaging|cellular imaging]].<ref>{{cite journal |title=Design and Use of Fluorescent Fusion Proteins in Cell Biology |author=Erik Snapp |journal=Current Protocols in Cell Biology |volume=27 |pages=21.4.1–21.4.13 |date=July 2005 | doi= 10.1002/0471143030.cb2104s27 |pmc=2875081 |pmid =18228466}}</ref><ref>{{cite journal |title= Imaging proteins inside cells with fluorescent tags |author1=Georgeta Crivat |author2=Justin W. Taraska |journal=Trends in Biotechnology|date=January 2012 |volume= 30|issue=1|pages=8–16|pmc=3246539|pmid=21924508|doi=10.1016/j.tibtech.2011.08.002}}</ref>