Burkholderia oklahomensis agglutinin is a canonical two‐domain OAA‐family lectin: structures, carbohydrate binding and anti‐HIV activity

Abstract

Burkholderia oklahomensis EO147 agglutinin (BOA) is a 29 kDa member of the OAA family of lectins. Members of the OAA family recognize high-mannose glycans and, by binding to the HIV envelope glycoprotein 120 (gp120), block the virus from binding to and entering the host cell, thereby inhibiting infection. OAA-family lectins comprise either one or two homologous domains, with a single domain possessing two glycan binding sites. We solved the structure of BOA in the ligand-free form as well as in complex with four molecules of 3α,6α-mannopentaose, the core unit of the N-linked high-mannose structures found on gp120 in vivo. This is the first structure of a double-domain OAA lectin in which all four binding sites are occupied by ligand. The structural details of the BOA-glycan interactions presented here, along with the determination of affinity constants and HIV inactivation data, shed further light onto the structure-function relationship in this important class of anti-HIV proteins.

Biological activity, cDNA cloning and primary structure of lectin KSA-2 from the cultivated red alga Kappaphycus striatum (Schmitz) Doty ex Silva

“…In the present study, we have determined the primary structure of KSA-2, and confirmed that it strongly resembles those of lower organisms, such as OAA from O. agardhii Sato and Hori, 2009), ESA-2 from E. serra , EDA-2 from E. denticulatum (Hung et al, 2015), MBHA from M. xanthus (Romeo et al, 1986;Koharudin et al, 2012), BOA from B. oklahomensis (Whitley et al, 2013) and PFL from P. fluorescens Pf0-1 (Sato et al, 2012) (Fig. 4), including its molecular size and the presence of tandemly repeated motifs.…”

“…This lectin family includes: OAA from Oscillatoria agardhii NIES-240 Sato and Hori, 2009;Koharudin et al, 2011), PFL from Pseudomonas fluorescens Pf0-1 (Sato et al, 2012), MBHA from Myxococcus xanthus (Koharudin et al, 2012), BOA from Burkholderia oklahomensis (Whitley et al, 2013), KAA-2 from Kappaphycus alvarezii (Sato et al, 2011a), BCA from Boodlea coacta (Sato et al, 2011b) and ESA-2 from Eucheuma serra (Sato et al, 2015). All of them share binding specificity for high-mannose N-glycans and have commonly two or four tandem repeats consisting of highly conserved sequences, which may lead to subtle difference in the degree of inhibiting activities.…”

Anti-influenza virus activity of high-mannose binding lectins derived from genus Pseudomonas

“…Recently, antiviral activities of those lectins have been widely investigated specially in algal lectins: cyanovirin-N (CV-N) derived from cynobacterium Nostoc ellipsosporum, cynobacterium Oscillatoria agardhii agglutinin (OAA), Burkholderia oklahomensis agglutinin (BOA) and griffithsin (GRFT) from a red alga Griffithsia sp. (Balzarini, 2007;Franç ois and Balzarini, 2012;Huskens and Schols, 2012;Whitley et al, 2013). These lectins that specifically bind to highmannose glycan on viral envelope have been shown to inhibit infection of HIV (Boyd et al, 1997;Mori et al, 2005;Férir et al, 2014) as well as other enveloped viruses, including influenza virus , hepatitis C virus (Helle et al, 2006;Kachko et al, 2013), Ebola virus (Barrientos et al, 2003(Barrientos et al, , 2004, herpesvirus 6 (Dey et al, 2000), measles virus (Dey et al, 2000), coronaviruses (van der Meer et al, 2007;O'Keefe et al, 2010), and Japanese encephalitis virus (Ishag et al, 2013).…”

Sampling of Glycan‐Bound Conformers by the Anti‐HIV Lectin Oscillatoria agardhii agglutinin in the Absence of Sugar

“…In addition, the X-ray data of sugar-free OAA suggests structural flexibility in binding site 2 (Figure S6), and inspection of additional X-ray structures that are available for several OAA homologues, with high conservation of binding site residues and sugar-protein interactions [6–7] , reveals that the sugar-bound conformation is frequently seen in sugar-free structures, reinforcing the notion that the bound conformation is more favorable in solution. This agrees with the observation that the motion between the ground and excited state detected by CPMG relaxation dispersion experiments, which occurs on a slower time scale than what is observed in the NOE data, does not coincide with that between free and bound conformations, extracted from chemical shift differences in the two 1 H- 15 N HSQC spectra.…”

“…[1–5] In particular, the OAA carbohydrate recognition epitope on a high-mannose glycan was identified as 3α,6α–mannopentaose (the branched core unit of Man-9), which is a unique recognition element to OAA family lectins compared to all other anti-HIV lectins. [2,6–7] The X-ray crystal structures of both free and glycan-bound OAA revealed a β-barrel-like structure with two symmetrically positioned glycan binding sites at opposite ends of the barrel. [3] In the presence of sugar, the protein structure in binding site 2 shows a conformational change, namely the orientation of the peptide bond between W77 and G78 is flipped by ~180°.…”