Analysis of the interaction between the HIV-inactivating protein cyanovirin-N and soluble forms of the envelope glycoproteins gp120 and gp41.
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.
O'Keefe
B R
BR
Laboratory of Drug Discovery Research and Development, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, SAIC Frederick, Frederick Cancer Research and Development Center, Frederick, Maryland, USA.
Shenoy
S R
SR
Xie
D
D
Zhang
W
W
Muschik
J M
JM
Currens
M J
MJ
Chaiken
I
I
Boyd
M R
MR
D019380:Anti-HIV Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001426:Bacterial Proteins; D001667:Binding, Competitive; D015374:Biosensing Techniques; D002151:Calorimetry; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002942:Circular Dichroism; D005454:Fluorescence Polarization; D006678:HIV / Q000187:drug effects*; D015699:HIV Envelope Protein gp120 / Q000378:metabolism* / Q000494:pharmacology; D015700:HIV Envelope Protein gp41 / Q000378:metabolism* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013997:Time Factors
D019380:Anti-HIV Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41; D011994:Recombinant Proteins; C107733:cyanovirin N