Team:Queens Canada/Background

Biosensors are devices that are able to detect the presence of analytes and effectively convert this biological response to an electrical signal. This system consists of three components: a bioreceptor, transducer and detector. The bioreceptor is able to form substrate-specific interactions with the analyte. The transducer is then able to detect the substrate-receptor interaction and transmit this into an electrical signal, which is amplified and processed by the detector. This information is then capable of being sent to a data storage device for quantification and analytical purposes.

Ligand Binding Domain

Nuclear receptors are a family of evolutionarily conserved proteins that functions as a ligand-dependent transcription factor [1]. After binding certain ligands, the receptor undergoes a conformational change which activates them, and allows them to bind directly to DNA to alter gene transcription [1]. Circulating steroid hormones, like cortisol, are able to activate the receptor and mediate processes such as stress response, energy metabolism and immune responses [2]. The ligand binding domain of nuclear receptors generally consists of eleven alpha-helices and two beta-sheets that enable the formation of a three-layered protein structure [2]. There also exists a regulatory C-terminal helix, titled "helix 12”, that is essential for hormone binding. There are conserved residues within these helices which form critical interactions with the ligand allowing for specificity within the interaction [2].

The above image demonstrates the generic structure of the apo-LBD (unbound) and holo-LBD (Ligand bound) conformations of a nuclear receptor. Large structural homology in nuclear receptors allows for the potential ability to modularly exchange the ligand binding domain of our biosensor in order to measure a vast array of different analytes. Both of the detection methods we have developed utilize conformational changes in the nuclear receptor ligand binding domain to produce a measurable signal.

Approaches

Starting with the natural Ligand Binding Domain of nuclear receptors as our means of binding to ligands, we took two approaches to producing a measurable signal from this interaction.
Please click here to see our approaches and design process.



References
  1. T. Kino, Glucocorticoid Receptor. MDText.com, Inc., 2000.
  2. H. Reyer, S. Ponsuksili, E. Kanitz, R. Pöhland, K. Wimmers, and E. Murani, “A Natural Mutation in Helix 5 of the Ligand Binding Domain of Glucocorticoid Receptor Enhances Receptor-Ligand Interaction,” PLoS One, vol. 11, no. 10, p. e0164628, Oct. 2016.