Anti-HIV activity of defective cyanovirin-N mutants is restored by dimerization.
Cyanovirin-N (CV-N) is a two-domain, cyanobacterial protein that inhibits human immunodeficiency virus (HIV) at nanomolar concentrations by binding to high mannose sugars on the HIV envelope glycoprotein gp120. The wild type protein can exist as a monomer or a domain-swapped dimer with the monomer and dimer containing two or four sugar binding sites, respectively, one on each domain. Here we demonstrate that monomeric, single binding site mutants are completely inactive and that a single site, whether located on domain A or B, is insufficient to impart the antiviral activity. Linking inactive, monomeric proteins in a head-to-head fashion by an intermolecular disulfide bond or by creating an exclusively domain-swapped dimer via a hinge residue deletion restored antiviral activity to levels similar to that of wild type CV-N. These findings demonstrate unequivocally that multisite binding by CV-N type lectins is necessary for viral inhibition.
Department of Structural Biology, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15260, USA.
Elena
E
Matei
Andrew
A
Zheng
William
W
Furey
Jeremy
J
Rose
Christopher
C
Aiken
Angela M
AM
Gronenborn
D019380:Anti-HIV Agents / Q000378:metabolism* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D015699:HIV Envelope Protein gp120 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D008358:Mannose / Q000378:metabolism*; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary
D019380:Anti-HIV Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D015699:HIV Envelope Protein gp120; C514793:gp120 protein, Human immunodeficiency virus 1; C107733:cyanovirin N; D008358:Mannose