National Center for
3S5X: Structure Of The Cyanobacterial Oscillatoria Agardhii Agglutinin (oaa) In Complex With A3,a6 Mannopentaose
Structure (2011) 19 p.1170-1181» All references (2)
The cyanobacterial Oscillatory Agardhii agglutinin (OAA) is a recently discovered HIV-inactivating lectin that interacts with high-mannose sugars. Nuclear magnetic resonance (NMR) binding studies between OAA and alpha3,alpha6-mannopentaose (Manalpha(1-3)[Manalpha(1-3)[Manalpha(1-6)]Manalpha(1-6)]Man), the branched core unit of Man-9, revealed two binding sites at opposite ends of the protein, exhibiting essentially identical affinities. Atomic details of the specific protein-sugar contacts in the recognition loops of OAA were delineated in the high-resolution crystal structures of free and glycan-complexed protein. No major changes in the overall protein structure are induced by carbohydrate binding, with essentially identical apo- and sugar-bound conformations in binding site 1. A single peptide bond flip at W77-G78 is seen in binding site 2. Our combined NMR and crystallographic results provide structural insights into the mechanism by which OAA specifically recognizes the branched Man-9 core, distinctly different from the recognition of the D1 and D3 arms at the nonreducing end of high-mannose carbohydrates by other antiviral lectins.