Physicochemical characterization of the recombinant lectin scytovirin and microbicidal activity of the SD1 domain produced in rice against HIV‑1
Authors/Creators
- 1. Department of Plant Production and Forestry Science, School of Agrifood and Forestry Science and Engineering, University of Lleida-Agrotecnio CERCA Center, 25198 Lleida, Spain
- 2. Frederick National Laboratory for Cancer Research, Leidos Biomedical Research Inc., Frederick, MD 21702, USA,; Molecular Targets Program, Center for Cancer Research, National Cancer Institute, NIH, Frederick, MD, USA
- 3. IrsiCaixa AIDS Research Institute, 08916 Badalona, Spain
- 4. IrsiCaixa AIDS Research Institute, 08916 Badalona, Spain; Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, 08916 Badalona, Spain
- 5. siCaixa AIDS Research Institute, 08916 Badalona, Spain
- 6. siCaixa AIDS Research Institute, 08916 Badalona, Spain; Germans Trias i Pujol Research Institute (IGTP), Can Ruti Campus, 08916 Badalona, Spain; Chair of AIDS and Related Diseases, University of Vic-Central University of Catalonia, 08500 Vic, Barcelona, Spain
- 7. Molecular Targets Program, Center for Cancer Research, National Cancer Institute, NIH, Frederick, MD, USA; Natural Products Branch, Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, NIH, Frederick, MD, USA
- 8. Department of Plant Production and Forestry Science, School of Agrifood and Forestry Science and Engineering, University of Lleida-Agrotecnio CERCA Center, 25198 Lleida, Spain; Catalan Institute for Research and Advanced Studies (ICREA), 08010 Barcelona, Spain
Description
Key message Rice-produced SD1 retains its physicochemical properties and provides efficient pre-exposure HIV-1
prophylaxis against infection in vitro.
Abstract Scytovirin (SVN) is an HIV-neutralizing lectin that features two structural domains (SD1 and SD2) that bind to
HIV-1 envelope glycoproteins. We expressed SD1 in rice seeds as a potential large-scale production platform and confirmed
that rice-derived SD1 binds the HIV-1 envelope glycoprotein gp120 in vitro. We analyzed the thermodynamic properties of
SD1 compared to full-size SVN (produced in E. coli) by isothermal titration and differential scanning calorimetry to characterize
the specific interactions between SVN/SD1 and gp120 as well as to high-mannose oligosaccharides. SVN bound with
moderate affinity (
Kd = 1.5 μM) to recombinant gp120, with 2.5-fold weaker affinity to nonamannoside (
Kd of 3.9 μM), and
with tenfold weaker affinity to tetramannoside (13.8 μM). The melting temperature (
Tm) of full-size SVN was 59.1 °C and
the enthalpy of unfolding (ΔHunf) was 16.4 kcal/mol, but the Tm
fell when SVN bound to nonamannoside (56.5 °C) and twice
as much energy was required for unfolding (ΔHunf = 33.5 kcal/mol). Interestingly, binding to tetramannoside destabilized the
structure of SD1 (ΔTm ~ 11.5 °C) and doubled the enthalpy of unfolding, suggesting a dimerization event. The similar melting
phenomenon shared by SVN and SD1 in the presence of oligomannose confirmed their conserved oligosaccharide-binding
mechanisms. SD1 expressed in transgenic rice was able to neutralize HIV-1 in vitro. SD1 expressed in rice, therefore, is
suitable as a microbicide component.
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