Analysis of protein‐protein interactions between isoforms of malate dehydrogenase and citrate synthase

Abstract

Sequential enzymes involved in a metabolic pathway are often found in specific and dynamic protein‐protein interactions. The assembly of proteins into this metabolon allow the efficient transfer of substrate between adjacent proteins increasing the throughput and decreasing the potential for side metabolic reactions to occur between competing enzymes. One such pairing is the malate dehydrogenase (MDH) and citrate synthase (CS). In the forward direction of the tricarboxylic cycle, the oxidation of malate to OAA catalyzed by MDH is thermodynamically unfavorable. Coupling and potentially direct shuttling of product‐substrate affords the cycle to continue. The interaction site between mitochondrial MDH and CS has been partially identified via computational docking and cross‐linking studies. However, the domains and key residues of interaction and their impact on the actions and affinity of various isoforms of MDH and CS have not been identified. Using two biophysical techniques, protein thermal melts and surface plasminogen resonance, we have found both mitochondrial and cytosolic human MDH interact with CS (mitochondrial 3 fold greater than cytosolic), while plant MDH shows no interaction. Traditional pulldowns were used in addition to biophysical techniques. Using molecular crowding agents, we have identified the affinity and stoichiometry of interactions. This will allow us to probe the structures for key residues of interaction in the future.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.