Protein adenylyltransferase FICD (FICD)

Protein which can both mediate the addition of adenosine 5'-monophosphate (AMP) to certain residues of target proteins (AMPylation), and also the removal of the identical modification from target proteins (de-AMPylation), depending on the context (By similarity). The side chain of Glu-231 determines which of the two opposing activities (AMPylase or de-AMPylase) will occur (By similarity).

Acts as a key regulator of the ERN1/IRE1-mediated unfolded protein response (UPR) by mediating AMPylation or p - AMPylation of HSPA5/BiP (PubMed:25601083). In unstressed cells, functions as an adenylyltransferase by mediating AMPylation of HSPA5/BiP in'Thr-518', thereby inactivating it (By similarity).