Amino acid sequence analysis of the N proteins from a variety of coronavirus  (SARS-CoV and Human-CoV OC43) strain suggest  that a highly conserved structure within NTD domain  and SR-rich region and the 3D structure of the protein of SARS-coronaviruses and Human-CoV OC43 are available. They selected these proteins as template proteins  for homology model of the SR-rich region MHV N protein. After all, this model protein has 53-230 amino acids site, which included NTD and SR-rich region.