Part:BBa_K2710005

His-IaaH-SpyTag

6xHis IaaH with Spy-Tag

Usage and Biology

Indole-3-acetamide hydrolase is an enzyme involved in the biosynthesis of indole-3-aectic acid.

The auxin indole-3-acetic acid, is a plant hormone involved in the regulation of plant growth and development¹. Indole-3-aecetic acid can be synthesised via the indole-3-acetamide pathway, which converts tryptophan to indole-3-aectic acid in a two-step enzymatic pathway². The flavoprotein tryptophan 2-monooxygenase (IaaM) catalyses the oxidative decarboxylation of tryptophan to indole-3-acetamide in the first, rate limiting step of the pathway³. Subsequently, the enzyme indole-3-acetamide hydrolase (IaaH) converts indole-3-acetamide to indole-3-aectic acid⁴.

Indole-3-acetamide hydrolase originating from Alcaligenes sp. strain HPC127114 was fused with a SpyTag and a hexahistidine tag (his tag).

The SpyTag forms one component of the SpyTag/SpyCatcher system, which enables covalent attachment of two proteins⁵. The SpyTag and SpyCatcher system was created by cleaving the CnaB2 domain of the fibronectin-binding protein FbaB derived from Streptococcus pyogenes to form a thirteen residue SpyTag peptide and a 116-residue SpyCatcher peptide⁵. The SpyTag (1.1 kDa) and SpyCatcher (12 kDa) form an irreversible intramolecular isopeptide bond between Asp¹¹⁷ on SpyTag and Lys³¹ on SpyCatcher⁵, spontaneously and specifically binding to each other so that they can be used as attachment mechanisms to create new, self-assembling protein arrangements⁶.

It is particularly useful because neither component needs to be at the C or N terminus⁶, and the effect on the attached protein’s activity appears to be negligible10. It also reported as useful in a variety of reaction conditions, with Howarth showing that the SpyTag/SpyCatcher “had a high yield...required only simple mixing (and) tolerated diverse conditions (pH, buffer components and temperature)”⁷.

A 6x his tag (six consecutive histidine residues, also known as a hexahistidine tag) was added to IaaH to enable purification using Immobilised Metal Affinity Chromatography (IMAC) columns⁸.

They are small metal-chelating tags of five or six consecutive histidine residues which can be expressed onto other proteins by fusing them to their N or C terminus⁹. They have “minimal effect on [protein] tertiary structure and biological activity” depending on location and are “easy and specific to remove”¹⁰. Histidine was chosen specifically because it has the “strongest interactions with metal ion matrices” but these interactions can be disrupted using pH or imidazole¹⁰.

Often this is done in order to make protein purification of recombinant proteins easier, because His-tagged proteins can be selected from many others using a ‘His-trap’ (metal affinity chromatography)⁸. This tag works because the hexahistidine binds to the metals Cu2+, Co2+, Zn2+ and Ni2+, and as a result, the selected proteins expressing the His-tag can be isolated because they alone are supposed to remain bound to the metal of the column or surface⁹. The selection of His rich proteins produced by certain expression strains (e.g. Escherichia coli) can prove more difficult if the concentration produced of the desired protein is very small, and the strain has many His-rich proteins¹¹.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  INCOMPATIBLE WITH RFC[21]

  Illegal BglII site found at 1128
  
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 661
  
• 1000
  COMPATIBLE WITH RFC[1000]

References

1. Davies, P. J. Plant Hormones: Biosynthesis, Signal Transduction, Action! , (Springer Netherlands, 2007).
2. Spaepen, S., Vanderleyden, J. & Remans, R. Indole-3-acetic acid in microbial and microorganism-plant signaling. FEMS Microbiol Rev 31, 425-448, doi:10.1111/j.1574-6976.2007.00072.x (2007).
3. Gaweska, H. M., Taylor, A. B., Hart, P. J. & Fitzpatrick, P. F. Structure of the flavoprotein tryptophan 2-monooxygenase, a key enzyme in the formation of galls in plants. Biochemistry 52, 2620–6 (2013).
4. Mishra, P., Kaur, S., Sharma, A. N. & Jolly, R. S. Characterization of an Indole-3-Acetamide Hydrolase from Alcaligenes faecalis subsp. parafaecalis and Its Application in Efficient Preparation of Both Enantiomers of Chiral Building Block 2,3-Dihydro-1,4-Benzodioxin-2-Carboxylic Acid. PLoS One 11, e0159009 (2016).
5. Zakeri, B. et al. Peptide tag forming a rapid covalent bond to a protein, through engineering a bacterial adhesin. Proc Natl Acad Sci U S A 109, E690-697, doi:10.1073/pnas.1115485109 (2012).
6. Domeradzka, N. E., Werten, M. W., Wolf, F. A. & de Vries, R. Protein cross-linking tools for the construction of nanomaterials. Curr Opin Biotechnol 39, 61-67, doi:10.1016/j.copbio.2016.01.003 (2016).
7. Reddington, S. C. & Howarth, M. Secrets of a covalent interaction for biomaterials and biotechnology: SpyTag and SpyCatcher. Curr Opin Chem Biol 29, 94-99, doi:10.1016/j.cbpa.2015.10.002 (2015).
8. Hochuli, E., Dobeli, H. & Schacher, A. New metal chelate adsorbent selective for proteins and peptides containing neighbouring histidine residues. J Chromatogr 411, 177-184 (1987).
9. Lindner, P. et al. Specific detection of his-tagged proteins with recombinant anti-His tag scFv-phosphatase or scFv-phage fusions. Biotechniques 22, 140-149, doi:10.2144/97221rr01 (1997).
10. Terpe, K. Overview of tag protein fusions: from molecular and biochemical fundamentals to commercial systems. Appl Microbiol Biotechnol 60, 523-533, doi:10.1007/s00253-002-1158-6 (2003).
11. Andersen, K. R., Leksa, N. C. & Schwartz, T. U. Optimized E. coli expression strain LOBSTR eliminates common contaminants from His-tag purification. Proteins 81, 1857-1861, doi:10.1002/prot.24364 (2013).

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