The following summary Table 2 has comments on the status of exposure of the tryptophan and surrounding residues, and on the involvement in binding based on alignments with the Zhang-Yap analysis.
Table 2 Sialic acid binding scores and surface exposure of tryptophan -containing subsequences.
Subsequence Protein GenBank or PDB entry Score Experimental observation or exposure suggested by structural analogy
FFSNVTWFHAIHVSGTN SARS-CoV-2 S1-NTD MN908947.3 0.88 Tryptophan exposed
FYSNVTGFHTIHTFGNP SARS-CoV S1-NTD NP_828851.1 0.82 Site aligning with above, no tryptophan, exposed
SNIIRGWIFGTTLDSKT SARS-CoVS1-NTD MN908947.3 0.71 Example of buried Tryptophan, but possibly accessible at base of cleft
HDGGKTWHSAATAIYCA neuraminidase Influenza B PDB 1NSB 0.94 Tryptophan exposed
EGKQGNFKNLREFVFKN SARS-CoV-2 S1-NTD MN908947.3 0.47 Aligns with a Zhang-Yap binding site
SEKSGNFKHLREFVFKN SARS-CoVS1-NTD NP_828851.1 0.53 Aligns with a Zhang-Yap binding site
KAGNSIFRSFHFTDFYN Hemagglutinin esterase PDB 3CL5 0.88 Aligns with a Zhang-Yap binding site
SAGDSIFKSYHFTRFYN CoV - E3 PDB 4EB1.1 0.82 Aligns with a Zhang-Yap binding site
GDSSSGWTAGAAAYYVG SARS-CoV-2 MN908947.3 0.94 Aligns with a Zhang-Yap binding site
SPAQDIWGTSAAAYFVG SARS-CoB NP_828851.1 0.82 Aligns with a Zhang-Yap binding site
SGSNDIWMQNKGLFYTQ Hemagglutinin esterase PDB 3CL5 0.71 Aligns with Zhang-Yap binding site
NGSNDVWIFNKVRFYRA CoV - E3 Q14EB1.1 0.71 Aligns with Zhang-Yap binding site