Editing Protein production (section)

==== Bacterial systems ====

===== ''Escherichia coli'' =====
[[File:E. coli Bacteria (7316101966).jpg|thumb|right|''E. coli'', one of the most popular hosts for artificial gene expression.]]
''[[Escherichia coli|E. coli]]'' is one of the most widely used expression hosts, and DNA is normally introduced in a [[plasmid]] expression vector. The techniques for overexpression in ''E. coli'' are well developed and work by increasing the number of copies of the gene or increasing the binding strength of the promoter region so assisting transcription.<ref name=":1" />

For example, a DNA sequence for a protein of interest could be [[cloning#Cloning in biology|cloned]] or [[subcloning|subcloned]] into a high copy-number plasmid containing the ''[[lac operon|lac]]'' (often [[LacUV5]]) promoter, which is then [[transformation (genetics)|transformed]] into the bacterium ''E. coli''. Addition of [[IPTG]] (a [[lactose]] analog) activates the lac promoter and causes the bacteria to express the protein of interest.<ref name="pmid10508629" />

''E. coli'' strain BL21 and BL21(DE3) are two strains commonly used for protein production. As members of the B lineage, they lack ''[[Lon protease family|lon]]'' and ''[[OmpT]]'' proteases, protecting the produced proteins from degradation. The DE3 prophage found in BL21(DE3) provides [[T7 RNA polymerase]] (driven by the LacUV5 promoter), allowing for vectors with the T7 promoter to be used instead.<ref>{{cite journal |last1=Jeong |first1=H |last2=Barbe |first2=V |last3=Lee |first3=CH |last4=Vallenet |first4=D |last5=Yu |first5=DS |last6=Choi |first6=SH |last7=Couloux |first7=A |last8=Lee |first8=SW |last9=Yoon |first9=SH |last10=Cattolico |first10=L |last11=Hur |first11=CG |last12=Park |first12=HS |last13=Ségurens |first13=B |last14=Kim |first14=SC |last15=Oh |first15=TK |last16=Lenski |first16=RE |last17=Studier |first17=FW |last18=Daegelen |first18=P |last19=Kim |first19=JF |title=Genome sequences of Escherichia coli B strains REL606 and BL21(DE3). |journal=Journal of Molecular Biology |date=11 December 2009 |volume=394 |issue=4 |pages=644–52 |doi=10.1016/j.jmb.2009.09.052 |pmid=19786035}}</ref>

===== ''Corynebacterium'' =====
Non-pathogenic species of the gram-positive ''[[Corynebacterium]]'' are used for the commercial production of various amino acids. The ''[[Corynebacterium glutamicum|C. glutamicum]]'' species is widely used for producing [[glutamate]] and [[lysine]],<ref>{{cite journal | vauthors = Brinkrolf K, Schröder J, Pühler A, Tauch A | title = The transcriptional regulatory repertoire of Corynebacterium glutamicum: reconstruction of the network controlling pathways involved in lysine and glutamate production | journal = Journal of Biotechnology | volume = 149 | issue = 3 | pages = 173–82 | date = September 2010 | pmid = 19963020 | doi = 10.1016/j.jbiotec.2009.12.004 }}</ref> components of human food, animal feed and pharmaceutical products.

Expression of functionally active human [[epidermal growth factor]] has been done in ''C. glutamicum'',<ref>{{cite journal | vauthors = Date M, Itaya H, Matsui H, Kikuchi Y | title = Secretion of human epidermal growth factor by Corynebacterium glutamicum | journal = Letters in Applied Microbiology | volume = 42 | issue = 1 | pages = 66–70 | date = January 2006 | pmid = 16411922 | doi = 10.1111/j.1472-765x.2005.01802.x | doi-access = free }}</ref> thus demonstrating a potential for industrial-scale production of human proteins. Expressed proteins can be targeted for secretion through either the general, [[secretory pathway]] (Sec) or the [[twin-arginine translocation pathway]] (Tat).<ref>{{cite journal | vauthors = Meissner D, Vollstedt A, van Dijl JM, Freudl R | title = Comparative analysis of twin-arginine (Tat)-dependent protein secretion of a heterologous model protein (GFP) in three different Gram-positive bacteria | journal = Applied Microbiology and Biotechnology | volume = 76 | issue = 3 | pages = 633–42 | date = September 2007 | pmid = 17453196 | doi = 10.1007/s00253-007-0934-8 | s2cid = 6238466 }}</ref>

Unlike [[gram-negative bacteria]], the gram-positive ''Corynebacterium'' lack [[lipopolysaccharides]] that function as antigenic [[endotoxins]] in humans.{{cn|date=January 2024}}

===== ''Pseudomonas fluorescens'' =====
The non-pathogenic and gram-negative bacteria, ''[[Pseudomonas fluorescens]]'', is used for high level production of recombinant proteins; commonly for the development bio-therapeutics and vaccines. ''P. fluorescens'' is a metabolically versatile organism, allowing for high throughput screening and rapid development of complex proteins. ''P. fluorescens''  is most well known for its ability to rapid and successfully produce high titers of active, soluble protein.<ref>{{cite journal | vauthors = Retallack DM, Jin H, Chew L | title = Reliable protein production in a Pseudomonas fluorescens expression system | journal = Protein Expression and Purification | volume = 81 | issue = 2 | pages = 157–65 | date = February 2012 | pmid = 21968453 | doi = 10.1016/j.pep.2011.09.010 }}</ref>