1XD6

Crystal structures of novel monomeric monocot mannose-binding lectins from Gastrodia elata

Summary for 1XD6

• Entry DOI: 10.2210/pdb1xd6/pdb
• Related: 1XD5
• Descriptor: gastrodianin-4, SULFATE ION (3 entities in total)
• Functional Keywords: monocot mannose-binding lectin, monomer, homogeneous beta-sheet, antifungal protein
• Biological source: Gastrodia elata
• Total number of polymer chains: 1
• Total formula weight: 12345.60

Authors

Liu, W.,Yang, N.,Wang, M.,Huang, R.H.,Hu, Z.,Wang, D.C. (deposition date: 2004-09-04, release date: 2005-01-11, Last modification date: 2024-10-23)

Primary citation

Liu, W.,Yang, N.,Ding, J.,Huang, R.H.,Hu, Z.,Wang, D.C.
Structural Mechanism Governing the Quaternary Organization of Monocot Mannose-binding Lectin Revealed by the Novel Monomeric Structure of an Orchid Lectin
J.Biol.Chem., 280:14865-14876, 2005

PubMed Abstract: Two isoforms of an antifungal protein, gastrodianin, were isolated from two subspecies of the orchid Gastrodia elata, belonging to the protein superfamily of monocot mannose-specific lectins. In the context that all available structures in this superfamily are oligomers so far, the crystal structures of the orchid lectins, both at 2.0 A, revealed a novel monomeric structure. It resulted from the rearrangement of the C-terminal peptide inclusive of the 12th beta-strand, which changes from the "C-terminal exchange" into a "C-terminal self-assembly" mode. Thus, the overall tertiary scaffold is stabilized with an intramolecular beta-sheet instead of the hybrid observed on subunit/subunit interface in all known homologous dimeric or tetrameric lectins. In contrast to the constrained extended conformation with a cis peptide bond between residues 98 and 99 commonly occurring in oligomers, a beta-hairpin forms from position 97 to 101 with a normal trans peptide bond at the corresponding site in gastrodianin, which determines the topology of the C-terminal peptide and thereby its unique fold pattern. Sequence and structure comparison shows that residue replacement and insertion at the position where the beta-hairpin occurs in association with cis-trans inter-conversion of the specific peptide bond (97-98) are possibly responsible for such a radical structure switch between monomers and oligomers. Moreover, this seems to be a common melody controlling the quaternary states among bulb lectins through studies on sequence alignment. The observations revealed a structural mechanism by which the quaternary organization of monocot mannose binding lectins could be governed. The mutation experiment performed on maltose-binding protein-gastrodianin fusion protein followed by a few biochemical detections provides direct evidence to support this conclusion. Potential carbohydrate recognition sites and biological implications of the orchid lectin based on its monomeric state are also discussed in this paper.

PubMed: 15649901
DOI: 10.1074/jbc.M411634200

Experimental method

X-RAY DIFFRACTION (2 Å)