Part:BBa_K4160003

RR120 VHH

RR120 VHH is a camelid heavy chain antibody raised against the azo dye RR120 (Figure 1). In the presence of RR120, the RR120 VHH domains dimerize.¹

Figure 1 | Chemical structure of RR120 azo dye. Image derived from Villabona et al., 2020.²

The TU-Eindhoven team 2022 fused the RR120 VHH to the EpoR (BBa_K4160001) to generate the GEMS receptor (BBa_K4160008). In the presence of azo dye RR120, the GEMS receptor homodimerizes and activates downstream signaling.³

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]

Usage and Biology

Camelid antibodies include a unique class of immunoglobulins, consisting of functional antibodies that are composed exclusively of heavy chains (Figure 2).⁴ These heavy-chain antibodies do not contain the first domain of the constant region, since it is sliced out during mRNA processing. In addition, the antigen-binding site of heavy-chain antibodies solely consists of a single variable domain which is referred to as VHH (or nanobody).⁴

Figure 2 | Camelid and human antibodies. Human mAB conventional antibodies are composed of two heavy and two light chains. The ligand is recognized by a variable domain of both the heavy and the light chain. Camelid hcAb are heavy chain antibodies in which the ligand is recognized by a variable domain of only one heavy chain. A recombinant VHH domain (nanobody) consists of only a single VHH domain. Image derived from Bannas et al., 2017.⁵

VHHs are beneficial due to their small size, high solubility, and high stability, allowing them to penetrate tissue in vivo easily. VHH domains of camelid heavy chain antibodies have evolved around 50 million years to acquire these characteristics.5 Nanobodies are modular and can be genetically linked to toxins, Fc-domains, other VHH domains, and peptide tags. In addition, they can be chemically linked to drugs, nanoparticles, radionuclides, and photosensitizers. Hence, nanobodies can be tailored depending on the therapeutic purpose.⁵ Because VHHs are largely stable and can penetrate tissue more easily than large mAb, they are used for effectively targeting tumors in vivo.⁵

GEMS receptor

TU-Eindhoven 2022 used this part as an affinity domain for the Generalized Extracellular Molecule Sensor (GEMS) receptor (BBa_K4160008). Upon binding of RR120 to the RR120 VHH affinity domains, the GEMS receptor dimerizes and induces the JAK/STAT pathway (Figure 3).³

Figure 3 | Activation of GEMS receptor containing an RR120 VHH domain. In the presence of azo dye RR120, the GEMS receptor activates through a conformational change between the two receptor subunits.

Characterization

Characterization of RR120 VHH as an affinity domain of the GEMS receptor can be found on the BBa_K4160008 page.

References

1. Spinelli S, Tegoni M, Frenken L, Van Vliet C, Cambillau C. Lateral recognition of a dye hapten by a llama VHH domain. J Mol Biol. 2001;311(1):123-129. doi:10.1006/JMBI.2001.4856
2. Villabona-Leal EG, Escobar-Villanueva AG, Ovando-Medina VM, et al. Semiconducting polypyrrole@TiO2 pure anatase nanoparticles for photodegradation of reactive red 120 azo dye. J Mater Sci Mater Electron. 2020;31(15):12178-12190. doi:10.1007/S10854-020-03764-2
3. Scheller L, Strittmatter T, Fuchs D, Bojar D, Fussenegger M. Generalized extracellular molecule sensor platform for programming cellular behavior article. Nat Chem Biol. 2018;14(7):723-729. doi:10.1038/s41589-018-0046-z
4. Recombinant Anti-Dye hapten RR120 VHH Single Domain Antibody (A52) - Creative Biolabs. Accessed October 3, 2022. https://www.creativebiolabs.net/Anti-Dye-hapten-RR120-VHH-Single-Domain-Antibody-24028.htm
5. Recombinant Anti-Dye hapten RR120 VHH Single Domain Antibody (A52) - Creative Biolabs. Accessed October 3, 2022. https://www.creativebiolabs.net/Anti-Dye-hapten-RR120-VHH-Single-Domain-Antibody-24028.htm