Difference between revisions of "Help:Tag"

(Introduction to Tags)
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[[Image:Part icon tag.png]]
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#redirect [[Help:Proteins]]
<small>Browse [https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=Tag Tag parts]!</small>
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<hr>
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==Introduction to Tags==
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[https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=Tag (Degradation) tags] are genetic additions to the end of a sequence which modify expressed proteins in different ways such as marking the protein for faster degradation (see below).
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Tags are also used for binding various particles in solution (making them easier to purify in solution from other proteins in a cell).  Famous examples of the latter are the [http://en.wikipedia.org/wiki/His-tag "His Tag"] (which binds to Nickel or Cobalt) and the [http://www-users.med.cornell.edu/~jawagne/FLAG-tag.html "FLAG tag"] (which binds to an "AntiFLAG" antibody), both of which are commercially available.
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==Degradation Tags==
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These genetic tags mark a protein for degradation, thus decreasing a protein's half life (see each tag's specifications for their respective half lives). 
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One of the useful aspects of genetic tags is the ability to detect gene activity in a time-sensitive manner.
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Tags can be found on:
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* [[Image:Part icon reporter.png]][https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=reporter Reporters],
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* [[Image:Part icon cds.png]][https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=coding Protein Coding parts],
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* [[Image:Part icon generator.png]][https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=generator Protein Generators], and
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* [[Image:Part icon inverter.png]][https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=inverter Inverters].<br>
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''Note'': Tags cannot currently be used as [[An Introduction to BioBricks|Biobricks]] because currently all of our [https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=Coding Protein Coding parts] end in the double stop codon "<b>TAATAA</b>".
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===Mechanism of Use===
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Currently all of our [https://parts.igem.org/cgi/partsdb/pgroup.cgi?pgroup=Tag Tags] operate through the use of protein-degrading enzymes (proteases) within the cell. 
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They do so by coding for a sequence of about eleven amino acids at the C-terminus of a protein.  This sequence is read by a special type of RNA known as ssRA ("small stable RNA A"), and then degraded by the proteases ClpXP or ClpAP in e.coli (no such system is yet known for yeast).
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Although originally the number of amino acids encoding for a ssRA tag was ''eleven'' (the first sequence that encoded for destruction via ssRA tagging was <b>AANDENYALAA</b> by [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8584937 Keiler et al]), a subsequent study by [http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=9603842 Andersen et al] tested the efficacy of mutating only the last ''three'' amino acids of that system.  Thus our tags (<b>AAV, ASV, LVA, LAA</b>) are classified by only three amino acids.
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===Future Plans===
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Our future plans for tags involve building proteins using biobricks.  To read more on this project, visit [https://dspace.mit.edu/handle/1721.1/32535 Ira Phillip's work on biobrick modification].
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===References===
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# Jabri and Nature News.  "Tag, you're degraded". 2003.  [http://www.nature.com/nsmb/journal/v10/n9/full/nsb0903-676.html article]
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# Karzai, AW.  "The SsrA−SmpB system for protein tagging, directed degradation and ribosome rescue".  2000. [http://www.nature.com/nsmb/journal/v7/n6/full/nsb0600_449.html Review Article]
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# Keiler, KC et al.  "Role of a peptide tagging system in degradation of proteins synthesized from damaged messenger RNA."  1996. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8584937 Pubmed]
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# Andersen, JB et al.  "New Unstable Variants of Green Fluorescent Protein for Studies of Transient Gene Expression in Bacteria".  1998.  [http://www.pubmedcentral.gov/articlerender.fcgi?tool=pubmed&pubmedid=9603842 link]
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Latest revision as of 21:40, 15 June 2017

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