nsp3aUB1

The sequence of the N-terminal domain of nsp3 (1-183) is highly conserved in different SARS coronavirus species but shows less than 25% of sequence identity with other known proteins. This region exhibits two well defined regions with different physico-chemical and structural properties. Its N-terminus (1-110) exhibits an ubiquitin-like fold with two additional helices which make the overall structure of this domain (UB1 domain) more elongated than other ubiquitin-like proteins. The C-terminal domain (110-183; AC domain) is rich in glutamic acid residues (38%) and is structurally disordered.

The functional significance of RNA-binding by this domain is unknown. It possesses a ubiquitin fold, as does the domain N-terminal to the PLP domain. It is unclear if this relationship has any functional significance with respect to full-length SARS-nsp3. The predicted function of this domain based on its similarity to Ras-binding proteins and ISG15 remains to be experimentally validated.

Prentice E, McAuliffe J, Lu X, Subbarao K, Denison MR. Identification and characterization of severe acute respiratory syndrome coronavirus replicase proteins.  J Virol. 2004 Sep;78(18):9977-86.

Kanjanahaluethai A, Chen Z, Jukneliene D, Baker SC. Membrane topology of murine coronavirus replicase nonstructural protein 3.  Virology. 2007 Jan 11;

Stertz S, Reichelt M, Spiegel M, Kuri T, Martinez-Sobrido L, Garcia-Sastre A, Weber F, Kochs G. The intracellular sites of early replication and budding of SARS-coronavirus. Virology. 2007 Jan 5

Graham RL, Denison MR. Replication of murine hepatitis virus is regulated by papain-like proteinase 1 processing of nonstructural proteins 1, 2, and 3. J Virol. 2006 Dec;80(23):11610-20.