@article {152150, title = {Sequence of the SARS-CoV-2 Spike Transmembrane Domain Encodes Conformational Dynamics.}, journal = {J Phys Chem B}, volume = {129}, year = {2025}, month = {2024 Dec 18}, pages = {194-209}, abstract = {

The homotrimeric SARS-CoV-2 spike protein enables viral infection by undergoing a large conformational transition, which facilitates the fusion of the viral envelope with the host cell membrane. The spike protein is anchored to the SARS-CoV-2 envelope by its transmembrane domain (TMD), composed of three TM helices, each contributed by one of the protomers of spike. Although the TMD is known to be important for viral fusion, whether it is a passive anchor of the spike or actively promotes fusion remains unknown. Specifically, it is unclear if the TMD and its dynamics facilitate the prefusion to postfusion conformational transition of the spike. Here, we computationally study the dynamics and self-assembly of the SARS-CoV-2 spike TMD in homogeneous POPC and cholesterol containing membranes. Atomistic simulations of a long TM helix-containing protomer segment show that the membrane-embedded segment bobs, tilts and gains and loses helicity, locally thinning the membrane. Coarse-grained multimerization simulations using representative TM helix structures from the atomistic simulations exhibit diverse trimer populations whose architecture depends on the structure of the TM helix protomer. While a symmetric conformation reflects the symmetry of the resting spike, an asymmetric TMD conformation could promote membrane fusion through the stabilization of a fusion intermediate. Together, our simulations demonstrate that the sequence and length of the SARS-CoV-2 spike TM segment make it inherently dynamic, that trimerization does not abrogate these dynamics and that the various observed TMD conformations may enable viral fusion.

}, issn = {1520-5207}, doi = {10.1021/acs.jpcb.4c05270}, author = {Lall, Sahil and Balaram, Padmanabhan and Mathew, M K and Gosavi, Shachi} } @article {137335, title = {Niacinamide enhances cathelicidin mediated SARS-CoV-2 membrane disruption.}, journal = {Front Immunol}, volume = {14}, year = {2023}, month = {2023}, pages = {1255478}, abstract = {

The continual emergence of SARS-CoV-2 variants threatens to compromise the effectiveness of worldwide vaccination programs, and highlights the need for complementary strategies for a sustainable containment plan. An effective approach is to mobilize the body{\textquoteright}s own antimicrobial peptides (AMPs), to combat SARS-CoV-2 infection and propagation. We have found that human cathelicidin (LL37), an AMP found at epithelial barriers as well as in various bodily fluids, has the capacity to neutralise multiple strains of SARS-CoV-2. Biophysical and computational studies indicate that LL37{\textquoteright}s mechanism of action is through the disruption of the viral membrane. This antiviral activity of LL37 is enhanced by the hydrotropic action of niacinamide, which may increase the bioavailability of the AMP. Interestingly, we observed an inverse correlation between LL37 levels and disease severity of COVID-19 positive patients, suggesting enhancement of AMP response as a potential therapeutic avenue to mitigate disease severity. The combination of niacinamide and LL37 is a potent antiviral formulation that targets viral membranes of various variants and can be an effective strategy to overcome vaccine escape.

}, keywords = {Antimicrobial Cationic Peptides, Antiviral Agents, Cathelicidins, COVID-19, Humans, Niacinamide, SARS-CoV-2}, issn = {1664-3224}, doi = {10.3389/fimmu.2023.1255478}, author = {Bhatt, Tanay and Dam, Binita and Khedkar, Sneha Uday and Lall, Sahil and Pandey, Subhashini and Kataria, Sunny and Ajnabi, Johan and Gulzar, Shah-E-Jahan and Dias, Paul M and Waskar, Morris and Raut, Janhavi and Sundaramurthy, Varadharajan and Vemula, Praveen Kumar and Ghatlia, Naresh and Majumdar, Amitabha and Jamora, Colin} } @article {77446, title = {Mechanistic Insights into an Unusual Side-Chain-Mediated N-C Bond Cleavage under Collision-Induced Dissociation Conditions in the Disulfide-Containing Peptide Conopressin.}, journal = {J Am Soc Mass Spectrom}, volume = {31}, year = {2020}, month = {2020 May 06}, pages = {1083-1092}, abstract = {

Conopressin, a nonapeptide disulfide CFIRNCPKG amide present in cone snail venom, undergoes a facile cleavage at the Cys6-Pro7 peptide bond to yield a disulfide bridged ion. Analysis of the mass spectral fragmentation pattern reveals the presence of a major fragment ion, which is unambiguously assigned as the tripeptide sequence IRN amide. The sequence dependence of this unusual fragmentation process has been investigated by comparing it with the fragmentation patterns of related peptides, oxytocin (CYIQNCPLG amide), Lys-vasopressin (CYFQNCPKG amide), and a series of synthetic analogues. The results establish the role of the Arg4 residue in facilitating the unusual N-C bond cleavage at Cys6. Structures are proposed for a modified disulfide bridged fragment containing the Cys1 and Cys6 residues. Gas-phase molecular dynamics simulations provide evidence for the occurrence of conformational states that permit close approach of the Arg4 side chain to the Cys6 C methylene protons.

}, issn = {1879-1123}, doi = {10.1021/jasms.0c00023}, author = {Kumar, Sanjeev and Venkatesha, M Achanna and Lall, Sahil and Prakash, Sunita and Balaram, Padmanabhan} }