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

Burkholderiaoklahomensis EO147 agglutinin (BOA) is a 29kDa member of the Oscillatoriaagardhii agglutinin (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 3,6-mannopentaose, the core unit of the N-linked high-mannose structures found on gp120 invivo. This is the first structure of a double-domain OAA-family lectin in which all four binding sites are occupied by ligand. The structural details of the BOAglycan interactions presented here, together with determination of affinity constants and HIV inactivation data, shed further light onto the structurefunction relationship in this important class of anti-HIV proteins. Database The atomic coordinates and structure factors for ligand-bound and ligand-free BOA have been deposited into the Protein Data Bank under accession numbers 4GK9 and 4GU8, respectively.