DNA Origami Assembly for the Tar Chemoreceptor

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This project centers around the idea of using DNA origami to assemble the Tar chemoreceptor. This assembly method would provide novel opportunities to investigate how this receptor works previously untestable using other assembly methods.

Introduction to Chemotaxis

Chemotaxis is the process by which bacteria sense chemicals in their environment. This is done through the use of chemoreceptors to sense a chemical gradient that they can follow towards higher concentrations of food or away from higher concentrations of poisons or other unfavorable conditions. The Tar chemoreceptor is involved with the sensing of aspartate, a common amino acid, by binding aspartate in the extracellular portion of the protein and then propagates a signal down the receptor to activate a pathway to alter movement.

Possible Applications of Chemotaxis

Understanding how signals are propagated in chemotaxis would be incredibly helpful in the fight against antibiotic resistance. Being able to control bacterial movement could allow a treatment to be engineered to move bacteria either towards antibiotics, therefore reducing the necessary dosage, or away from food or nutrients, effectively starving the bacteria. In addition, being able to use bacteria as carriers for drugs could also be a novel drug delivery technique.

DNA Origami

This project involves using a DNA tetrahedron as a scaffold for the Tar chemoreceptor complex in vitro. In this model, receptor dimers are attached at three vertices of the DNA tetrahedron to make the native structure seen in vivo. At the other end of the receptor, two proteins are shown: CheA, a kinase, shown in blue, and CheW, a coupling protein, shown in cyan.

Attachment to DNA

The protein receptor dimer is using NTA-functionalized DNA. This means that the DNA has an NTA, or nitrilotriaceticacid, is able to coordinate with nickel ions, shown in green, which is also able to coordinate with histidines. The Tar chemoreceptor has six histidines added to the N-terminus of the protein in vitro, which should be able to coordinate with the nickel ion as well, creating a coordination complex. One of monomers, shown in black, in each dimer is coordinated with the nickel atom.

Significance of Assembly Method

This assembly method will allow this receptor to be investigated in ways not previously possible. These ways include expanding the trimer of dimers by changing the size of the DNA tetrahedron as well as having more control of dimer position in the trimer of dimers. With these new experiments possible, more information can be gained about bacterial movement.