Identification of an Intrinsically Disordered Region (IDR) in Arginyltransferase 1 (ATE1)

Arginyltransferase 1 (ATE1) catalyzes arginylation, an important posttranslational modification (PTM) in eukaryotes that plays a critical role in cellular homeostasis. The disruption of ATE1 function is implicated in mammalian neurodegenerative disorders and cardiovascular maldevelopment, while posttranslational arginylation has also been linked to the activities of several important human viruses such as SARS-CoV-2 and HIV. Despite the known significance of ATE1 in mammalian cellular function, past biophysical studies of this enzyme have mainly focused on yeast ATE1, leaving the mechanism of arginylation in mammalian cells unclear. In this study, we sought to structurally and biophysically characterize mouse (<i>Mus musculus</i>) ATE1. Using size-exclusion chromatography (SEC), small-angle X-ray scattering (SAXS), and hydrogen-deuterium exchange mass spectrometry (HDX-MS), assisted by AlphaFold modeling, we found that mouse ATE1 is structurally more complex than yeast ATE1. Importantly, our data indicate the existence of an intrinsically disordered region (IDR) in all mouse ATE1 splice variants. However, comparative HDX-MS analyses show that yeast ATE1 does not have such an IDR, consistent with prior X-ray, cryo-EM, and SAXS analyses. Furthermore, bioinformatics approaches reveal that mammalian ATE1 sequences, as well those as in a large majority of other eukaryotes, contain an IDR-like sequence positioned in proximity to the ATE1 GNAT active-site fold. Computational analysis suggests that the IDR facilitates the formation of a complex between ATE1 and tRNA^Arg, adding a new complexity to the ATE1 structure and providing new insights for future studies of ATE1 functions.