Portal de Periódicos da CAPES

Selective Interactions of the Human Immunodeficiency Virus-Inactivating Protein Cyanovirin-N with High-Mannose Oligosaccharides on gp120 and Other Glycoproteins

2001; American Society for Pharmacology and Experimental Therapeutics; Volume: 297; Issue: 2 Linguagem: Inglês

10.1016/s0022-3565(24)29588-4

1521-0103

Shilpa R. Shenoy, Barry R. O’Keefe, Anders Bolmstedt, Laura K. Cartner, Michael R. Boyd,

Glycosylation and Glycoproteins Research

The virucidal protein cyanovirin-N (CV-N) mediates its highly potent anti-human immunodeficiency virus activity, at least in part, through interactions with the viral envelope glycoprotein gp120. Here we dissect in further detail the mechanism of CV-N's glycosylation-dependent binding to gp120. Isothermal titration calorimetry (ITC) binding studies of CV-N with endoglycosidase H-treated gp120 showed that binding was completely abrogated by removal of high-mannose oligosaccharides from the glycoprotein. Additional ITC and circular dichroism spectral studies with CV-N and other glycoproteins as well showed that CV-N discriminately bound only glycoproteins that contain high-mannose oligosaccharides. Binding experiments with RNase B indicated that the single high-mannose oligosaccharide on that enzyme mediated all of its binding with CV-N (K(d) = 0.602 microM). A finer level of oligosaccharide selectivity of CV-N was revealed in affinity chromatography-liquid chromatography-mass spectrometry experiments, which showed that CV-N preferentially bound only oligomannose-8 (Man-8) and oligomannose-9 isoforms of RNase B. Finally, we biophysically characterized the interaction of CV-N with a purified, single oligosaccharide, Man-8. The binding affinity of Man-8 for CV-N is unusually strong (K(d) = 0.488 microM), several hundredfold greater than observed for oligosaccharides and their protein lectins (K(d) = 1 microM--1 mM), further establishing a critical role of high-mannose oligosaccharides in CV-N binding to glycoproteins.