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1.  Crystallization and preliminary X-ray crystallographic analysis of a galactose-specific lectin from Dolichos lablab  
The galactose-specific lectin from the seeds of a leguminous plant, D. lablab, has been crystallized. Molecular-replacement solution using 3.0 Å X-ray diffraction data showed the lectin to be a tetramer.
The galactose-specific lectin from the seeds of Dolichos lablab has been crystallized using the hanging-drop vapour-diffusion technique. The crystals belong to space group P1, with unit-cell parameters a = 73.99, b = 84.13, c = 93.15 Å, α = 89.92, β = 76.01, γ = 76.99°. X-ray diffraction data to a resolution of 3.0 Å have been collected under cryoconditions (100 K) using a MAR imaging-plate detector system mounted on a rotating-anode X-ray generator. Molecular-replacement calculations carried out using the available structures of legume lectins as search models revealed that the galactose-specific lectin from D. lablab forms a tetramer similar to soybean agglutinin; two such tetramers are present in the asymmetric unit.
PMCID: PMC2150945  PMID: 16511291
Dolichos lablab; galactose-specific lectins; legume lectins
2.  N- and C-Terminal Cooperation in Rotavirus Enterotoxin: Novel Mechanism of Modulation of the Properties of a Multifunctional Protein by a Structurally and Functionally Overlapping Conformational Domain 
Journal of Virology  2006;80(1):412-425.
Rotavirus NSP4 is a multifunctional endoplasmic reticulum (ER)-resident nonstructural protein with the N terminus anchored in the ER and about 131 amino acids (aa) of the C-terminal tail (CT) oriented in the cytoplasm. Previous studies showed a peptide spanning aa 114 to 135 to induce diarrhea in newborn mouse pups with the 50% diarrheal dose approximately 100-fold higher than that for the full-length protein, suggesting a role for other regions in the protein in potentiating its diarrhea-inducing ability. In this report, employing a large number of methods and deletion and amino acid substitution mutants, we provide evidence for the cooperation between the extreme C terminus and a putative amphipathic α-helix located between aa 73 and 85 (AAH73-85) at the N terminus of ΔN72, a mutant that lacked the N-terminal 72 aa of nonstructural protein 4 (NSP4) from Hg18 and SA11. Cooperation between the two termini appears to generate a unique conformational state, specifically recognized by thioflavin T, that promoted efficient multimerization of the oligomer into high-molecular-mass soluble complexes and dramatically enhanced resistance against trypsin digestion, enterotoxin activity of the diarrhea-inducing region (DIR), and double-layered particle-binding activity of the protein. Mutations in either the C terminus, AAH73-85, or the DIR resulted in severely compromised biological functions, suggesting that the properties of NSP4 are subject to modulation by a single and/or overlapping highly sensitive conformational domain that appears to encompass the entire CT. Our results provide for the first time, in the absence of a three-dimensional structure, a unique conformation-dependent mechanism for understanding the NSP4-mediated pleiotropic properties including virus virulence and morphogenesis.
PMCID: PMC1317517  PMID: 16352566

Results 1-2 (2)