Crystal structures of SARS-CoV-2 ADP-ribose phosphatase (ADRP): from the apo form to ligand complexes

Among 15 nonstructural proteins (Nsps), the newly emerging SARS-CoV-2 encodes a large, multidomain Nsp3. One of its units is ADP-ribose phosphatase domain (ADRP, also known as macrodomain) which is believed to interfere with the host immune response. Such a function appears to be linked to the proteins ability to remove ADP-ribose from ADP-ribosylated proteins and RNA, yet the precise role and molecular targets of the enzyme remains unknown. Here, we have determined five, high resolution (1.07 - 2.01 [A]) crystal structures corresponding to the apo form of the protein and complexes with 2-(N-morpholino)ethanesulfonic acid (MES), AMP and ADPr. We show that the protein undergoes conformational changes to adapt to the ligand in a manner previously observed before for in close homologs from other viruses. We also identify a conserved water molecule that may participate in hydrolysis. This work builds foundations for future structure-based research of the ADRP, including search for potential antiviral therapeutics.