4.18. Scytovirin
It is a 95-amino-acid-long, 9.7 kDa polypeptide containing five intrachain disulfide bonds. It was first isolated from the aqueous extract of Scytonema varium. It binds to the envelope glycoprotein of HIV (gp120, gp160, and gp41) and inactivates the virus in low nanomolar concentrations.