Genomic screening and molecular dynamics simulations of cyanovirin-N homologs from cyanobacteria phylum

Isolation and structure elucidation of Dm-CVNH, a new cyanovirin-N homolog with activity against SARS-CoV-2 and HIV-1

An anti-HIV screen of natural product extracts resulted in the discovery of a new antiviral protein through bioassay-guided fractionation of an aqueous extract of the ascidian Didemnum molle. The protein was sequenced through a combination of tandem mass spectroscopy and N-terminal Edman degradation of peptide fragments after a series of endoproteinase digestions. The primary amino acid sequence and disulfide bonding pattern of the 102-amino acid protein were closely related to the antiviral protein cyanovirin-N (CV-N). This new CV-N homolog was named Dm-CVNH. Alphafold2 prediction resulted in a tertiary structure, highly similar to CV-N, comprised of two symmetrically related domains that contained five β-strands and two α-helical turns each. Dm-CVNH showed specificity for high mannose and oligomannose structures, bound to HIV-1 gp-120 and potently inactivated HIV in neutralization assays (EC50 of 0.95 nM). Dm-CVNH inhibited infection in a SARS-CoV-2 live virus assays and was shown to bind to the S1 domain of SARS-CoV-2 Spike glycoprotein. Dm-CVNH behaved in a manner similar to CV-N, binding with a 2:1 stoichiometry to Spike (both to WH-1 and Omicron variants) and preferring the Omicron variant (Kd 42 nM) to original WH-1 (Kd = 89 nM) Spike. This sensitivity to emergent strains was mirrored in viral neutralization assays where Dm-CVNH potently inhibited the infection of Omicron strains XBB.1.16 and JN.1 (IC50 = 11-18 nM).

Cyanobacterial secondary metabolites towards improved commercial significance through multiomics approaches

Cyanobacteria are ubiquitous photosynthetic prokaryotes responsible for the oxygenation of the earth's reducing atmosphere. Apart from oxygen they are producers of a myriad of bioactive metabolites with diverse complex chemical structures and robust biological activities. These secondary metabolites are known to have a variety of medicinal and therapeutic applications ranging from anti-microbial, anti-viral, anti-inflammatory, anti-cancer, and immunomodulating properties. The present review discusses various aspects of secondary metabolites viz. biosynthesis, types and applications, which highlights the repertoire of bioactive constituents they harbor. Majority of these products have been produced from only a handful of genera. Moreover, with the onset of various OMICS approaches, cyanobacteria have become an attractive chassis for improved secondary metabolites production. Also the intervention of synthetic biology tools such as gene editing technologies and a variety of metabolomics and fluxomics approaches, used for engineering cyanobacteria, have significantly enhanced the production of secondary metabolites.