Analysis of the Interaction between the HIV-Inactivating Protein Cyanovirin-N and Soluble Forms of the Envelope Glycoproteins gp120 and gp41

• Published in: Molecular pharmacology 2000-11, Vol.58 (5), p.982-992
• Main Authors: O'Keefe, Barry R., Shenoy, Shilpa R., Xie, Dong, Zhang, Wentao, Muschik, Jeffrey M., Currens, Michael J., Chaiken, Irwin, Boyd, Michael R.
• Format: Article
• Language: English
• Subjects: Anti-HIV Agents - antagonists & inhibitors; Anti-HIV Agents - pharmacology; Bacterial Proteins; Binding, Competitive; Biosensing Techniques; Calorimetry; Carrier Proteins - antagonists & inhibitors; Carrier Proteins - pharmacology; Circular Dichroism; Fluorescence Polarization; HIV - drug effects; HIV Envelope Protein gp120 - metabolism; HIV Envelope Protein gp120 - pharmacology; HIV Envelope Protein gp41 - metabolism; HIV Envelope Protein gp41 - pharmacology; Recombinant Proteins - metabolism; Spectrometry, Fluorescence; Time Factors
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.58.5.982

The novel virucidal protein cyanovirin-N (CV-N) binds with equally high affinity to soluble forms of either H9 cell-produced or recombinant glycosylated HIV-1 gp120 (sgp120) or gp160 (sgp160). Fluorescence polarization studies showed that CV-N is also capable of binding to the glycosylated ectodomain of the HIV-envelope protein gp41 (sgp41) (as well as SIV glycoprotein 32), albeit with considerably lower affinity than the sgp120/CV-N interaction. Pretreatment of CV-N with either sgp120 or sgp41 abrogated the neutralizing activity of CV-N against intact, infectious HIV-1 virions. Isothermal calorimetry and optical biosensor binding studies showed that CV-N bound to recombinant sgp120 with a K d value ranging from 2 to 45 nM and to sgp41 with a K d value of 606 nM; furthermore, they indicated an approximate 5:1 stoichiometry for CV-N binding to sgp120 and a 1:1 stoichiometry for CV-N binding to sgp41. Circular dichroism studies additionally illuminated the binding of CV-N with both sgp120 and sgp41, providing the first direct evidence that conformational changes are a consequence of CV-N interactions with both HIV-1 envelope glycoproteins.