(R1918) Sequence Conservation and Structural Modeling of an Arginyl-tRNA Transferase 1 (ATE1)

Nna-Emeka Ejimogu (University of Maryland Baltimore Country)| Verna Van (University of Maryland Baltimore Country)| Aaron Smith (University of Maryland Baltimore Country)

Arginyl-tRNATransferase 1 (ATE1) is a eukaryotic enzyme that arginylates cellular proteins, is an essential regulator of eukaryotic homeostasis via its involvement in the N-degron pathway, and regulates essential physiological processes such as embryogenesis, aging, cell migration, muscle contraction, and stress. Despite its importance, the structure, mechanism of action, and regulation of ATE1 has yet to be elucidated. The objective of this work is to model the three-dimensional fold of an ATE1, and to determine essential conserved residues that are involved in substrate recognition and enzymatic arginylation. In this study, we have modeled the structure of Saccharomyces cerevisiae ATE1 (ScATE1) and identified a putative location of the GCN5-related N-acetyl transferase (GNAT) fold, which is structurally conserved amongst amino-acid transferases. Additionally, we have performed a large-scale sequence alignment across eukaryotic ATE1s to map conserved residues onto our three-dimensional model. Notably, we have identified a highly-conserved His residue that would be consistent with the recognition of a negatively charged substrate and is located in a structural homologous site in bacterial amino-acid transferases. We hypothesize that this highly conserved (>90%) His residue is essential for substrate recognition, and site-directed mutagenesis is underway to verify this hypothesis. These results provide the first structural insights into the enzyme active site and mechanism of substrate recognition for ScATE1, and the strong sequence conservation suggest a common mode of action across eukaryotic homologs.