Structural genomics of the severe acute respiratory syndrome coronavirus: nuclear magnetic resonance structure of the protein nsP7

Here, we report the three-dimensional structure of severe acute respiratory syndrome coronavirus (SARS-CoV) nsP7, a component of the SARS-CoV replicase polyprotein. The coronavirus replicase carries out regulatory tasks involved in the maintenance, transcription, and replication of the coronavirus genome. nsP7 was found to assume a compact architecture in solution, which is comprised primarily of helical secondary structures. Three helices (2 to 4) form a flat up-down-up antiparallel -helix sheet. The N-terminal segment of residues 1 to 22, containing two turns of -helix and one turn of 310-helix, is packed across the surface of 2 and 3 in the helix sheet, with the -helical region oriented at a 60 ° angle relative to 2 and 3. The surface charge distribution is pronouncedly asymmetrical, with the flat surface of the helical sheet showing a large negatively charged region adjacent to a large hydrophobic patch and the opposite side containing a positively charged groove that extends along the helix 1. Each of these three areas is thus implicated as a potential site for protein-protein interactions. The severe acute respiratory syndrome coronavirus (SARS-CoV) most closely resembles the group II coronaviruses, which infect mice, rats, pigs, and humans (34). Upon viral entry, the 30-kb SARS-CoV genome is translated to produce a pre