Congratulations with the PhD degree Christa
Monday 3rd October DynaMo PhD scholar Christa Kanstrup defended her PhD thesis and was awarded the PhD degree with an excellent performance.
In front of a full auditorium of colleagues and friends, Christa Kanstrup successfully defended her PhD thesis entitled ‘Elucidation of the structure-function relationship in the Nitrate and Peptide Transporter Family’
Christa Kanstrup received the traditional PhD hat from her colleagues after the defence.
Summary
The Nitrate and Peptide transporter Family (NPF) are reported to have significant roles in nutrient use efficiency vital for agriculture, in transporting phytohormones essential for physiological processes in plants, and in transport of plant specialized metabolites – metabolites that can be both harmful and beneficial to humans. Even though this family is important, it is in many aspects unexplored.
In her PhD project, Christa sought to extend our knowledge on amino acid positions important for substrate specificity and transport rate in NPF transporters. She did so by adopting, the glucosinolate transporters 1-3 (GTR1-3) belonging to the NPFs, as a unique model system to investigate the molecular determinants of substrate specificity in the NPFs. GTR1 and GTR2 transport glucosinolates without any specific preference, whereas GTR3 prefers indolic glucosinolates. Following a rational mutagenic approach a distinct set of amino acids within the substrate binding cavity were shown to play a critical role in substrate specificity in the GTRs. In continuation Christa also investigated residues controlling transport rates in the NPF. Using a randomly found point mutation in GTR2, which installs hyperactivity, Christa performed extensive biophysical characterizations and found that the mutation lead to both changes in transport rate and in several other properties of the transporter including proton:glucosinolate stoichiometry, proton affinity and export ability. Lastly, Christa took first steps towards establishing high-throughput screening of GTR mutant libraries. Following the synthesis of seven different fluorescent glucosinolates by collaborators, Christa demonstrated transport of three of them by the GTR. This substrates lay the foundation for development of high-throughput screening assays for identification of additional amino acids important for substrate specificity and transport rate in the NPFs. Combined, the results presented in this dissertation provide first insights into the transport mechanism of the GTRs and lay the groundwork for further studies into the structure-function relationship in the NPFs.
Christa, who also did her MSc in the DynaMo Center will continue as postdoc in Associate Professor Hussam Nour-Eldins research group.