High-Mannose Specific Lectin and Its Recombinants from a Carrageenophyta Kappaphycus alvarezii Represent a Potent Anti-HIV Activity Through High-Affinity Binding to the Viral Envelope Glycoprotein gp120

• Published in: Marine biotechnology (New York, N.Y.) Vol. 18; no. 1; pp. 144 - 160
• Main Authors: Hirayama, Makoto, Shibata, Hiromi, Imamura, Koji, Sakaguchi, Takemasa, Hori, Kanji
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.02.2016; Springer Nature B.V
• Subjects: Algae; Anti-HIV Agents - administration & dosage; Anti-HIV Agents - chemistry; Anti-HIV Agents - metabolism; Binding Sites; Biomedical and Life Sciences; Biomedical research; Biotechnology; Cloning; Cyanobacteria; E coli; Economic importance; Engineering; Escherichia coli; Eucheuma serra; Freshwater & Marine Ecology; Glycoproteins; HIV; HIV - drug effects; HIV - physiology; HIV Envelope Protein gp120 - metabolism; Human immunodeficiency virus; Human immunodeficiency virus 1; Influenza; Kappaphycus alvarezii; Lectins; Life Sciences; Liquid chromatography; Mannose-Binding Lectins - administration & dosage; Mannose-Binding Lectins - genetics; Mannose-Binding Lectins - metabolism; Marine; Marine biology; Microbiology; Natural products; Original; Original Article; Oscillatoria agardhii; Peptides; Protein Binding; Protein Engineering - methods; Proteins; Reagents; Recombinant Proteins - administration & dosage; Recombinant Proteins - metabolism; Rhodophyta - genetics; Rhodophyta - metabolism; Studies; Ultrafiltration; Virus Internalization - drug effects; Viruses; West Nile virus; Zoology; Japan; Antiviral lectin; Carageenophyta; Alga; HIV; Kappaphycus alvarezii
• ISSN: 1436-2228; 1436-2236
• DOI: 10.1007/s10126-015-9677-1

We previously reported that a high-mannose binding lectin KAA-2 from the red alga Kappaphycus alvarezii, which is an economically important species and widely cultivated as a source of carrageenans, had a potent anti-influenza virus activity. In this study, the full-length sequences of two KAA isoforms, KAA-1 and KAA-2, were elucidated by a combination of peptide mapping and complementary DNA (cDNA) cloning. They consisted of four internal tandem-repeated domains, which are conserved in high-mannose specific lectins from lower organisms, including a cyanobacterium Oscillatoria agardhii and a red alga Eucheuma serra. Using an Escherichia coli expression system, an active recombinant form of KAA-1 (His-tagged rKAA-1) was successfully generated in the yield of 115 mg per liter of culture. In a detailed oligosaccharide binding analysis by a centrifugal ultrafiltration-HPLC method with 27 pyridylaminated oligosaccharides, His-tagged rKAA-1 and rKAA-1 specifically bound to high-mannose N-glycans with an exposed α1-3 mannose in the D2 arm as the native lectin did. Predicted from oligosaccharide binding specificity, a surface plasmon resonance analysis revealed that the recombinants exhibit strong interaction with gp120, a heavily glycosylated envelope glycoprotein of HIV with high association constants (1.48 − 1.61 × 10⁹ M⁻¹). Native KAAs and the recombinants inhibited the HIV-1 entry at IC₅₀s of low nanomolar levels (7.3–12.9 nM). Thus, the recombinant proteins would be useful as antiviral reagents targeting the viral surface glycoproteins with high-mannose N-glycans, and the cultivated alga K. alvarezii could also be a good source of not only carrageenans but also this functional lectin(s).