1dgw
From Proteopedia
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Structure of the rhombohedral crystal of canavalin from jack bean
Overview
The structure of canavalin, the vicilin-class storage protein from jack, bean, was refined to 1.7 A resolution in a highly twinned rhombohedral, crystal of space group R3 and unit-cell parameters a = b = c = 83.0 A, alpha = beta = gamma = 111.1 degrees. The resulting R and R(free) were, 0.176 and 0.245, respectively. The orthorhombic crystal structure (space, group C222(1), unit-cell parameters a = 136.5, b = 150.3, c = 133.4 A) was, also refined with threefold non-crystallographic symmetry restraints. R, and R(free) were 0.181 and 0.226, respectively, for 2.6 A resolution data., No significant difference in the protein structure was seen between these, two crystal forms, nor between these two and the hexagonal and cubic, crystal forms reported elsewhere [Ko et al. (1993), Acta Cryst. D49, 478-489; Ko et al. (1993), Plant Physiol. 101, 729-744]. A phosphate ion, was identified in the lumen of the C-terminal beta-barrel. Lattice, interactions showed that the trimeric molecule could be well accommodated, in both 'top-up' and 'bottom-up' orientations in a rhombohedral unit cell, of the R3 crystal and explained the presence of a high twin fraction. The, large inter-trimer stacking interface of the C222(1) crystal may account, for its relative stability. Atomic force microscopy (AFM) investigations, of the growth of three crystal forms of canavalin indicate the, rhombohedral form to be unique. Unlike the other two crystal forms, it, contains at least an order of magnitude more screw dislocations and, stacking faults than any other macromolecular crystal yet studied, and it, alone grows principally by generation of steps from the screw, dislocations. The unusually high occurrence of the screw dislocations and, stacking faults is attributed to mechanical stress produced by the, alternate molecular orientations in the rhombohedral crystals and their, organization into discrete domains or blocks. At boundaries of alternate, domains, lattice strain is relieved by the formation of the screw, dislocations.
About this Structure
1DGW is a Protein complex structure of sequences from Canavalia ensiformis with PO4 as ligand. Full crystallographic information is available from OCA.
Reference
X-ray diffraction and atomic force microscopy analysis of twinned crystals: rhombohedral canavalin., Ko TP, Kuznetsov YG, Malkin AJ, Day J, McPherson A, Acta Crystallogr D Biol Crystallogr. 2001 Jun;57(Pt 6):829-39. Epub 2001, May 25. PMID:11375502
Page seeded by OCA on Tue Nov 20 13:16:52 2007
