User:Conorrickard/Cyanovirin-N

The protein Cyanovirin-N (CV-N) and its bacterial origination N. ellipsosporum were screened for and discovered as being antiviral in the lab of Michael R. Boyd MD, PhD, University of South Alabama, 1997. It originally gained notable interest in its ostensible use as an antiviral topical agent to be applied before intercourse. It is antiviral against HIV-1, HIV-2, SIV, HCV, HSV-1, Influenza A and B, Ebola, and MARV.

Bacterial origin
Cyanobacteria, primary colonizers found mostly in ocean water, have evolved with many protective traits including antiviral activity. CV-N is a lectin protein produced by Nostoc ellipsosporum, a fresh water, gram negative, unbranched filamentous cyanobacteria.

Structure
The CV-N protein is made from 101 amino acids forming a monomer with two nearly identical domains hinged near the 50th amino acid. Torsion angle can separate the two domains, domains A and B. It is most often found in crystalized form to have been separated then reassociated with neighboring domains from the other separated monomers, repeatedly forming AB’ or BA’ pseudo-monomers also called domain-swapped dimers. CV-N is a mostly beta-sheet protein and its mass is 11 kilodaltons.

Its amino acid sequence is: LGKFSQTCYNSAIQGSVLTSTCERTNGGYNTSSIDLNSVIENVDGSLKWQPSNFIETCRNTQLAGSSELAAECKTRAQQFVSTKINLDDHIANIDGTLKYE



Mechanism against viruses
The CV-N lectin protein interacts with carbohydrates found on the surfaces of viruses. This halts their activity and ability to bind to target cell membranes.

The HIV envelope glycoprotein, gp120 contains high-mannose sugars. gp120 interacts with CD4 of the human T-cell and with gp140 fuses the viral and human menmbrane. Similarly, the SARS-CoV-2 envelope produces a spike protein with an S glycoprotein containing high-mannose sugars carrying out membrane fusion.

CV-N recognizes the N-linked high mannose sugars and interacts with Man-8 and Man-9 sugars. It is not known if both Man-8 and Man-9 are required or redundant.

Related
“While CVN was originally thought to be an orphan lectin with little homology to any other known protein family, a family of CVN homologs, termed CVNHs, has been described“.