Analysis of interaction between sulfated polysaccharides and HIV oligopeptides by surface plasmon resonance

This study aims to quantitatively investigate the interaction between sulfated polysaccharides with potent anti-HIV activity, dextran and curdlan sulfates with negatively charged sulfate groups, and poly-L-lysine as a model protein and oligopeptides from a HIV surface glycoprotein gp120 with positively charged amino acids using surface plasmon resonance (SPR) and dynamic light scattering (DLS) to elucidate the anti-HIV mechanism of sulfated polysaccharides. The apparent association- (k_a) and dissociation rate (k_d) constants of dextran and curdlan sulfates against poly-L-lysine were k_a = 6.92 × 10⁴-2.17 × 10⁶ 1/Ms and k_d = 4.29 × 10^-5-2.22 × 10^-4 1/s; these kinetic constants were dependent on the molecular weights and degree of sulfation of sulfated polysaccharides. For interaction, the three oligopeptides from the HIV gp120 were peptide A ²⁹⁷TRPNNNTRKRIRIQRGPGRA³¹⁶ with several lysine (K) and arginine (R) in the V3 loop region, peptide B ⁴⁹³PLGVAPTKAKRRVVQREKR⁵¹¹ with several K and R in the C-terminus region, and oligopeptide C ³⁶²KQSSGGDPEIVTHSFNCGG³⁸⁰ with few basic amino acids in the CD4 binding domain. Sulfated polysaccharides exhibited strong interaction against oligopeptides A and B, (k_a = 5.48 × 10⁴-2.96 × 10⁶ 1/Ms. and k_d = 1.74 × 10^-4-6.24 × 10^-3 1/s), no interaction was noted against oligopeptide C. Moreover, the particle size and zeta potential by DLS indicated the interaction between sulfated polysaccharides and oligopeptides A and B, suggesting the anti-HIV mechanism of sulfated polysaccharides to be the electrostatic interaction of negatively charged sulfated polysaccharides and HIV at the positively charged amino acid regions.