Elucidation Of Structural Domains Underlying Substrate Recognition In Plant Mate Transporters

The MATE (Multidrug And Toxic compound Extrusion) family of membrane transporters is found in all kingdoms of life. Many plant species harbor a large number of MATE genes. For example, there are as many as 58 different MATE genes in Arabidopsis thaliana alone, suggesting MATE transporter's involvement in a diverse array of biological processes. Most plant MATE proteins reported to-date transport a wide range of substrates coupled to cation (i.e., H+ or Na+) exchange. Based on the available functional data of plant MATE proteins, it can be broadly divided into two groups: those transporting common toxic compounds, and a unique group capable of transporting organic acids. Based on the correlations between these functional data and amino acid sequence similarities, we identified four major putative domains that dictate the differences in substrate recognition. We chose Sorghum bicolor MATE (Organic acid transporter) and Zea Mays MATE, as representative of organic acid and non-organic acid transporters, respectively to perform functional characterization of various chimeras where the different putative domains have been permutated. We use a combination of Rosetta homology modelling, imaging, and electrophysiology to investigate the potential role of each of the putative structural domains in determining plant MATE substrate recognition.