Protein domains/Affinity

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Protein tags and modifiers are short peptide sequences cloned in frame with protein coding sequences that change the protein's behavior. Affinity tags are generally appended to the N- or C-terminus of proteins to enable ready purification of the protein from cells.

Generally, cells expressing the protein fused to an affinity tag are pelleted, lysed, and applied to a column, resin or other solid support that displays a ligand to the affinity tags. The solid support is washed several times with buffer to eliminate unbound proteins. Then the protein of interest is eluted from the solid support via a buffer that causes the affinity tag to dissociate from the ligand resulting in a purified protein.

There are several different affinity tags available for purification. Each has benefits and advantages depending on your protein of interest and the cell from which you are purifying it.

Head domains

NameDescriptionColumn/resinAA sequenceLength
BBa_I712007c-Myc affinity tag  30
BBa_I712008HA affinity tag  30
BBa_K112703His affinity tag  21
BBa_K112705S affinity tag  48
BBa_K133035Methionine-His affinity tag   21
BBa_T20017x His tag head domain  27
BBa_T2004FLAG octapeptide head domain (DYKDDDDK)  30
BBa_T2007c-Myc head domain (EQKLISEEDL)  36
BBa_T2010hemagglutinin (HA) tag head domain (YPYDVPDYA)  33
BBa_T2013Strep-tag II head domain (WSHPQFEK)  30
BBa_T2016S-tag head domain (KETAAAKFERQHMDS)   51

Tail domains

NameDescriptionColumn/resinAA sequenceLength
BBa_J640053x FLAG affinity tag  81
BBa_K112503< myc ! in BBb  33
BBa_K112507< HA ! in BBb  33
BBa_K112601< AP tag ! in BBb  48
BBa_K112603< FLAG tag ! in BBb  27
BBa_K13190076xHis tag with double stop codon  24
BBa_K133036RGD-His affinity tag-Stop  30
BBa_K133133His affinity tag-stop  21
BBa_K525710DNA ligase from Escherichia coli (LigA) with PT7, RBS and His-tag  2064
BBa_T20007x His tag tail domain  27
BBa_T2003FLAG octapeptide tail domain (DYKDDDDK)  30
BBa_T2006c-Myc tail domain (EQKLISEEDL)  36
BBa_T2009hemagglutinin (HA) tag tail domain (YPYDVPDYA)  33
BBa_T2012Strep-tag tail domain (WRHPQFGG)  30
BBa_T2015S-tag tail domain (KETAAAKFERQHMDS)   51
BBa_T2021VSV-G epitope tag tail domain (YTDIEMNRLGK)  39

Internal domains

NameDescriptionColumn/resinAA sequenceLength
BBa_J32017S-Tag  46
BBa_K112502< myc > in BBb  30
BBa_K112506< HA > in BBb  30
BBa_K112602< FLAG tag > in BBb  24
BBa_K128000FLAG affinity tag  25
BBa_K128001HA affinity tag  27
BBa_K128005His affinity tag  18
BBa_K3765000SpyTag002  42
BBa_T20027x His tag special internal domain  21
BBa_T2005FLAG octapeptide special internal domain (DYKDDDDK)  24
BBa_T2008c-Myc special internal domain (EQKLISEEDL)  30
BBa_T2011hemagglutinin (HA) tag special internal domain (YPYDVPDYA)  27
BBa_T2014Strep-tag II special internal domain (WSHPQFEK)  24
BBa_T2017S-tag special internal domain (KETAAAKFERQHMDS)   45
BBa_T2022VSV-G epitope tag special internal domain (YTDIEMNRLGK)  33
BBa_T2025Glutathione S-transferase internal domain  657
BBa_T2028Chitin binding internal domain  156

Head or tail or internal

NameDescriptionColumn/resinAA sequenceLength
BBa_I757013His affinity tag  36
BBa_I757014Strep-Tag II affinity tag  24
BBa_J18909His tag (6xHis; E. coli - optimized)  18
BBa_J18916Strep tag II  24
BBa_J18917GST tag (E. coli)  687
BBa_J70620RFC12 Maltose Binding Protein Internal Domain [malE]   1140
BBa_K1404006p70-CsgA, curli generator  547
BBa_K1404007p70-CsgA-His, His-tagged curli generator  577
BBa_K1404008p70-CsgA-His*2, double His-tagged curli generator  607
BBa_K157011His affinity tag; Freiburg standard  18
BBa_K157012Strep affinity tag II; Freiburg standard  24
BBa_K2144101Vector containing Hisx6 and Sortase tag LPETGG  2117
BBa_K2812000Carbohydrate-binding domain from MpIBP  576
BBa_K3204001C-LytAm7 Affinity Polypeptide Tag  411
BBa_K376500310xHis Tag  30
BBa_K404211ViralBrick-587KO-His-Tag   105
BBa_K4359007V5 Tag  42
BBa_K4378000TphB: An effective overexpression casette   1080
BBa_K4422000Internal c-Myc (Pichia pastoris codon optimized)  30
BBa_K8230343x FLAG tag (Freiburg standard+RBS)  66
BBa_K823035HA-tag (Freiburg standard+RBS)  27
BBa_K823036cMyc-tag (Freiburg standard+RBS)  30
BBa_K82303710x His-tag (Freiburg standard+RBS)  30
BBa_K823038Strep-tag (Freiburg standard+RBS)  24
BBa_S04282K157011(His affinity tag; Freiburg standard):K157004(Fluorescin-A-binding )  548



  1. Kimple pmid=18429272
  2. Arnau pmid=16427311
  3. Azarkan pmid=17113368
  4. Waugh pmid=15922084