A group from Division of Plant Biology, Bose Institute, P/12 C.I.T. Scheme VII(M), Kolkata, 700054, India, etc. has reported that a unique mannose binding plant lectin from Narcissus tazetta bulb, NTL-125, could effectively inhibit SARS-CoV-2 replication in Vero-E6 cell line.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8988448/
A unique mannose binding plant lectin from Narcissus tazetta bulb named NTL-125 could inhibit SARS-CoV-2 replication in Vero-E6 cell line. The inhibitory concentration using Vero-E6 cells that reduced the SARS-CoV-2 viral entry by 50% (IC50) was approximately 0.8 µg/mL (i.e., 50 nM), and the cytotoxicity of NLE-125 on Vero-E6 cells was above 95% viable at 5 µg/mL and 85% viable at 10 µg/mL concentration.
The molecular docking studies revealed that thirty-six residues of RBD and 44 residues of NTL-125 were located within 5Å distance from each other in the complex whereas 27 residues of ACE-2 are in proximity to 32 residues of RBD. There are 17 common residues of RBD that interact with both ACE-2 and NTL-125. Among all these residues, for the RBD:NTL-125 complex, 10 of RBD and 11 of NTL-125 are within 3Å distance in the docked structure. For the RBD:ACE-2 complex, 9 residues of RBD and 9 residues of ACE-2 are within 3Å distance. NTL-125 occupies exactly the same region of the receptor binding motif (RBM) of the spike protein where hACE2 usually binds. As a result, the binding free energy change of NTL125–Spike protein interaction (-13.3 kcal/mol, kd ~0.41nM) is more negative than that between ACE2-Spike protein (-11.2 kcal/mol, kd ~12 nM) which clearly indicates that the former is more stable than the later.
Docking study confirmed further that the interaction between NTL-125-spike protein is also mediated through a S-protein glycan moiety, covalently linked to Asn165 of the spike protein and interacts with Ile137 and Thr138 of NTL-125 protein. Thus, the interaction between NTL-125-Spike is not only through amino acid residues but also through the glycan moieties.
