Dark Proteome of Newly Emerged SARS-CoV-2 in Comparison with Human and Bat Coronaviruses

Rajanish Giri; Taniya Bhardwaj; Meenakshi Shegane; Bhuvaneshwari R. Gehi; Prateek Kumar; Kundlik Gadhave

Membrane (M) glycoprotein plays an important role in virion assembly by interacting with the nucleocapsid (N) and E proteins [66] [67] [68] . Protein M interacts specifically with a short viral packaging signal containing coronavirus RNA in the absence of N protein, thereby highlighting an important nucleocapsid-independent viral RNA packaging mechanism inside the host cells [69] . It gains high-mannose N-glycans in ER, which are subsequently modified into complex N-glycans in the Golgi complex. Glycosylation of M protein is observed to be not essential for virion fusion in cell culture [70, 71] . Cryo-EM and Tomography data indicate that M forms two distinct conformations, a compact M protein having high flexibility and low spike density, and an elongated M protein having a rigid structure and narrow range of membrane curvature [72] . Some regions of M glycoproteins might serve as important dominant immunogens. Although no structural information is available for the full-length M protein as of yet, a short peptide of the membrane glycoprotein (residues 88-96) from Human SARS CoV was co-crystallized with a complex between A-2 alpha chain of the HLA class I histocompatibility antigen and β2microglobulin (PDB ID: 3I6G) [73] . Figure 5A shows that within this complex, the cocrystallized M protein region exists in an extended conformation. author/funder. All rights reserved. No reuse allowed without permission.