Sweet entanglements--protein:glycan interactions in two HIV-inactivating lectin families.

Structures and sugar binding by members of two lectin families, Cyanovirin-N homolog (CVNH) and Oscillatoria Agardhii agglutinin homolog (OAAH), were determined to elucidate the basis for recognition of high-mannose glycans on the HIV envelope glycoprotein gp120. We solved NMR solution and/or crystal structures for several lectins and delineated their carbohydrate specificity by array screening and direct NMR titrations. Both families recognize different epitopes on high-mannose glycans, namely, Manα(1-2)Man units at the end of the D1 and D3 arms and α3,α6-mannopentaose at the central branch point of Man-8 or Man-9 for CVNH and OAAH lectins, respectively.