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

The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.03.13.990598 doi: bioRxiv preprint Our analysis of the intrinsic disorder predisposition using six predictors revealed the mean PPID in ORF6 proteins of SARS-CoV-2, Human SARS, and Bat CoV to be 22.95%, 20.63%, and 20.63%, respectively ( Table 1) . Graphs in Figures 9A, 9B and 9C illustrate that ORF6 proteins from all three studied coronaviruses are expected to be moderately disordered proteins with the high disorder content in their C-terminal regions. These disordered regions are important for the biological activities of ORF6. As aforementioned, this hydrophilic region contains lysosomal targeting motif (YSEL) and diacidic motif (DDEE) responsible for binding and recognition during translocation [104] . However, the N-terminal region does not contain a noticeable disorder. The 1-38 residues of the N-terminal region of Human SARS CoV ORF6 was shown to be α-helical and embedded in the membrane, although ORF6 is not a transmembrane protein [106] . A long MoRF region ((residues 26-61 in SARS-CoV-2), (residues 31-63 in Human SARS), and (residues 30-60 in Bat Cov)) is also present at Cterminus of ORF6 proteins which are tabulated in Table 2 , and Supplementary Tables 7 and 8. No predictor other than MoRFchibi_web has located MoRFs in this protein. Supplementary Table 9 , 10, and 11 shows nucleotide-binding residues in ORF6 of all three viruses. It represents very few RNA binding residues by PPRint and few DNA binding residues by DRNApred.