Nutrient uptake and cell signaling are critical aspects for plant growth and development, and these molecules need to cross the cell membrane to reach their final destinations. In addition, in response to biotic or abiotic stresses, small molecules such as defense molecules or cuticle precursors need to be transported across the membrane to the surface of the plant. Both these activities require transporters to move small molecules from one side of the cell membrane to the other and ABC transporters are one of the most predominant transporters in plants. Plants have more ABC transporter genes compared to other living organisms, particularly for terrestrial plants in which ABC transporters likely played a role in allowing plants to adapt to dry land. Plant ABC transporters transport a variety of substrates including hormones, supportive materials (i.e. cuticle precursors), secondary metabolites, and toxic metals, among others, and mutations in these genes can cause detrimental effects on plant growth and development. Despite this importance, there are still few biochemical or structural studies of plant ABC transporters, likely due to their difficulty in expression and purification. These studies are important to address the gaps and unanswered questions left by reverse genetics approaches that established the framework in our understanding of plant ABC transporter function.

My lab uses a mixture of classical and modern membrane protein techniques for efficient and effective expression and purification of ABC transporters, and subsequently analyze the substrate specificity through in vitro assays and structure determination using single particle cryo-electron microscopy (cryoEM). In addition, my lab will use cryoEM to investigate the protein dynamics of both ABC transporters and several other dynamic protein complexes related to human health. These studies utilize the ability of cryoEM to capture several populations of protein conformations while using various data processing techniques to efficiently separate them out. Indeed, these heterogenous populations may represent intermediates in the conformational landscape or reveal critical aspects of protein dynamics that could increase our understanding of how protein structure determines function. Our goal with these studies, along with various computational strategies, is to push structural biology further from static snapshots of protein structures to reveal the dynamic motions of protein complexes.