1xd5
From Proteopedia
|
Crystal structures of novel monomeric monocot mannose-binding lectins from Gastrodia elata
Overview
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.
About this Structure
1XD5 is a Single protein structure of sequence from Gastrodia elata with SO4 as ligand. Full crystallographic information is available from OCA.
Reference
Structural mechanism governing the quaternary organization of monocot mannose-binding lectin revealed by the novel monomeric structure of an orchid lectin., Liu W, Yang N, Ding J, Huang RH, Hu Z, Wang DC, J Biol Chem. 2005 Apr 15;280(15):14865-76. Epub 2005 Jan 13. PMID:15649901
Page seeded by OCA on Sun Nov 25 01:54:09 2007
