The non-reducing manose is in contact through hydrogen bonding with a charged subsite (D37-K38) on the 2-fold-related subunit (A-B or C-D interfaces). The ligand is oriented with its reducing end positioned in the specificity pocket. The complete disaccharide molecule is visible in both subunits at site 3, which is the only extended site. The second subunit (C) shows a high degree of flexibility (Bav = 41.7 A2). Complexed disaccharide is responsible for the most crucial lattice contacts, which involve only one of the two independent subunits (A). The 3.0 A structure of the cubic Man-alpha 1,3-Man-OMe complex, determined by molecular replacement and refined with X-PLOR using NCS constraints and density modification methods, is less well ordered due to a high crystal solvent content (68%). In comparison, the A-B and C-D subunit pairs have narrow interfaces (476 A2) and no direct H-bond contacts. These subunit pairs (A-D and B-C) associate tightly with a buried surface area of 1738 A2 and 33 interchain hydrogen bonds resulting from C-terminal strand exchange. The highest occupied site is located in beta-sheet I (site 1), where interactions from the dimer-related subunit contribute to complex stabilization. The 12 bound methyl-alpha-Man molecules refined with B-factors < 22 A2 and occupancies in the range of 0.5 to 1.0. The four independent subunits (A, B, C and D) of the 222 tetramer and the three four-stranded beta-sheets (I,II and III) that constitute each subunit compare closely (r.m.s. The final model of the 2.29 A orthorhombic methyl-alpha-Man complex refined with an R-factor of 0.167 (all data) includes 12 bound sugar ligands and 327 water molecules. Crystal structures of GNA complexed with methyl-alpha-D-mannose (MeMan) and mannose-alpha 1,3-D-mannose-alpha-OMe (MeMan-2) have been determined and analyzed in terms of internal structural symmetry and saccharide binding. Galanthus nivalis agglutinin (GNA, a 50 kDa tetramer) is a mannose-specific lectin of the Amaryllidaceae family of bulb lectins. Diversity, Equity, Inclusion, and Access.Citation, Usage, Privacy Policies, Logo.Biologically Interesting Molecule Reference Dictionary (BIRD).
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