Mechanism of Covalent Flavin Attachment to Metabolic Enzyme Complex II
Complex II is an essential metabolic enzyme that functions in both the Krebs cycle and the electron transport chain in mitochondria, coupling succinate oxidation to fumarate with ubiquinone reduction to ubiquinol. Covalent FAD attachment in the flavoprotein subunit of this hetertrimeric complex is essential for succinate oxidation and mutations that abrogate this covalent linkage and result in pheochromocytoma-paraganglioma syndrome in humans have been identified, although the underlying biochemistry is currently undefined. In addition, assembly factors have recently been identified that are required for the covalent flavin attachment, and mutations in the assembly factors present with the same clinical symptoms as mutations in Complex II. Understanding the mechanism of covalent flavin attachment is vital to understanding the function of Complex II and how this unique enzyme has adapted utilization of an FAD cofactor to couple two essential respiratory processes. My work utilizes a combination of structural, biochemical and biophysical methods to investigate this mechanism, the underpinnings of which are highly conserved from bacteria to complex mammals. Mutagenesis and structural studies will also allow me to probe the role of specific mutations in Complex II malfunction in disease.