Argininosuccinate synthetase (ASS1) catalyzes a key step in both arginine biosynthesis and the urea cycle and is subject to activity regulation at the protein level. Multiple studies suggest that ASS1 activity can be modulated by distinct protein effectors and chemical modifications, including interactions with NMRAL1, the Bj-BPP-10c peptide, circadian regulator-associated post-translational modifications, and cysteine nitrosylation. While these findings suggest diverse activation and inhibition mechanisms, the structural and conformational bases of such regulation remain unknown. We propose to use a combination of steady-state enzymology, mutagenesis, and cryo-electron microscopy, to determine how these modulators reshape the ASS1 conformational landscape. Our initial studies indicate substrate-induced conformational changes, and our primary goal is to determine how protein-protein interactions and modifications further modulate enzyme conformation and catalysis. Defining these mechanisms will provide insight into metabolic control and may identify new opportunities for therapeutic intervention in nitrogen metabolism.
Abdallah et al. (Sun,) studied this question.