ADP-glucose pyrophosphorylase is central to starch synthesis in plants and glycogen synthesis in bacteria and other organisms, serving as carbon storage polymers. It is a common biotechnology target and an informed understanding of its regulation has implications for starch/glycogen synthesis in a host of organisms. Allosteric control of ADP-glucose pyrophosphorylase activity is an important but poorly understood regulatory mechanism. Presently it is unclear how the enzyme is allosterically activated and how that activation signal is transmitted structurally within the enzyme. The goal of this project is to perform computational, structural and biochemical studies to understand and characterize the allosteric signals and the interaction of the allosteric effectors on ADP-glucose pyrophosphorylase activity in bacteria as a model for plants. The PIs predict the presence of a common structural element that works as a switch but also the presence of an alternative allosteric signal binding site. This project will also contribute to education by training undergraduate and graduate students, establish international collaborations, and foster participation of underrepresented minorities in research by supporting programs such as McNair-SROP. This project will also support an international course on protein science that includes elements of the research, providing a unique training opportunity for undergraduate and graduate students.
Plant starch and bacterial glycogen biosynthetic pathways provide models for the structure and evolution of allosteric regulatory functions of the enzyme ADP-glucose pyrophosphorylase. Despite the importance of these pathways, the allosteric mechanism that controls the activity of this enzyme is largely unknown. The project comprises computational, structural, and biochemical studies to understand and characterize the transmission of the allosteric signal and the interaction of the allosteric effectors in the ADP-glucose pyrophosphorylase family. It is predicted there is both a common structural element that works as a switch and an alternative allosteric signal guided by a secondary site. Three main research objectives will be pursued: 1) screen several enzyme forms from diverse branches of the phylogenetic tree for the presence of a dual allosteric mechanism; 2) obtain crystal structures of allosteric mutants ("switched off") in several different conditions with different ligands to test the hypothesis that certain residues form a conserved allosteric switch in ADP-glucose pyrophosphorylases; and 3) perform computational studies (molecular dynamics, correlated movement analysis, and network pathway analysis) to predict the signaling pathways of activation from each putative allosteric site.
