Faculty Sponsor: Bryan Thurtle-Schmidt
Band 3, or Anion Exchanger 1, is the human bicarbonate transporter protein found in red blood cells that aids in cellular respiration. Bor1 is a borate transporter in plants, in the same family, with a similar sequence and structure to Band 3. It is responsible for transporting boron, an essential micronutrient in plants; in too high concentrations boron is toxic to the cell so its levels must be regulated. Determining similarities and differences between these proteins could support the use of Bor1 as a model for Band 3. Band 3 is known to be inhibited by a specific class of drugs and is also known to be a dimer inside cells. These traits were tested in S. cerevisiae yeast (Sc) with the Bor1 protein. The drugs SITS and DIDS are known to inhibit Band 3 transport by forming a covalent crosslink with a specific lysine residue. Through a genetic complementation assay, wild-type ScBor1 and constructs containing mutations in the lysine residue predicted to interact with the drugs were assessed for functionality. The results suggest that ScBor1 is not sensitive to this class of drug. Dimerization is another suspected similarity between Bor1 and Band 3 but in previous research ScBor1 has not yet been shown to be a dimer, unlike other borate transporters. A cross-linking assay was performed with ScBor1 incubated with yeast lipids to determine if lipids helped reconstitute dimerization, but the preliminary results were inconclusive. Further experiments should be conducted to determine if the protein truly integrated into the lipids or, since the detergent might interfere with the incorporation of protein into the liposomes, removing the detergent could better simulate a more native-like environment.