Crystal Structure of the Human, FIC-Domain Containing Protein HYPE and Implications for Its Functions

Protein AMPylation, the transfer of AMP from ATP to protein targets, has been recognized as a new mechanism of host-cell disruption by some bacterial effectors that typically contain a FIC-domain. Eukaryotic genomes also encode one FIC-domain protein, HYPE, which has remained poorly characterized. Here we describe the structure of human HYPE, solved by X-ray crystallography, representing the first structure of a eukaryotic FIC-domain protein. We demonstrate that HYPE forms stable dimers with structurally and functionally integrated FIC-domains and with TPR-motifs exposed for protein-protein interactions. As HYPE also uniquely possesses a transmembrane helix, dimerization is likely to affect its positioning and function in the membrane vicinity. The low rate of autoAMPylation of the wild-type HYPE could be due to autoinhibition, consistent with the mechanism proposed for a number of putative FIC AMPylators. Our findings also provide a basis to further consider possible alternative cofactors of HYPE and distinct modes of target-recognition. [Display omitted] •The first crystal structure of a eukaryotic FIC-domain protein is solved•Interdomain interactions and dimerization of HYPE result in a rigid structure•TPR-motifs and the active site of the autoinhibited FIC domain are exposed•In contrast to bacterial FICs, HYPE does not preferentially AMPylate small GTPases It is well established that posttranslational modifications (PTM) of proteins provide a key mechanism for control of functional states, protein-protein interactions, localization, and stability. Bunney et al. describe new insights into HYPE, the only human protein implicated in PTM by AMPylation.