Structure of 2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase from Pseudomonas putida

2-Keto-3-deoxy-6-phosphogluconate (KDPG) aldolase from Pseudomonas putida is a key enzyme in the Entner-Doudoroff pathway which catalyses the cleavage of KDPG via a class I Schiff-base mechanism. The crystal structure of this enzyme has been refined to a crystallographic residual R = 17.1% (R-free = 21.4%). The N-terminal helix caps one side of the torus of the (betaalpha)(8)-barrel and the active site is located on the opposite, carboxylic side of the barrel. The Schiff-base-forming Lys145 is coordinated by a sulfate (or phosphate) ion and two solvent water molecules. The interactions that stabilize the trimer are predominantly hydrophobic, with the exception of the cyclically permuted bonds formed between Glu132 OE1 of one molecule and Thr129 OG1 of a symmetry-equivalent molecule. Except for the N-terminal helix, the structure of KDPG aldolase from P. putida closely resembles the structure of the homologous enzyme from Escherichia coli.

Crystal structure of piratoxin-I: A calcium-independent, myotoxic phospholipase A(2)-homologue from Bothrops pirajai venom

The crystal structure of Piratoxin-I (PrTX-I) a Lys49 homologue isolated from the venom of Bothrops pirajai has been determined and refined at 2.8 Angstrom to a crystallographic residual of 19.7% (R-free = 29.7%). Amino-acid sequence differences between catalytically active phospholipases and PrTX-I in the putative Ca2+-binding loop, specifically the substitutions Tyr28-->Asn, Gly32-->Leu and Asp49-->Lys, result in an altered conformation of this loop, the analysis of the position of the E-amino group of Lys49 in the PrTX-I structure indicates that it fills the site normally occupied by the calcium ion in the catalytically active phospholipases, In contrast to the homologous monomeric Lys49 variant from Agkistrodon piscivorus piscivorus (App), PrTX-I is present as a dimer in the crystalline state, as observed in the structures of myotoxin II from Bothrops asper and Bothropstoxin I from Bothrops jararacussu. The two molecules in the asymmetric unit in the crystal structure of PrTX-I are related by a nearly perfect two-fold symmetry axis, yet the dimeric structure is radically different from the dimeric structure of the phospholipase from Crotalus atrox. In the C. atrox structure the dimer interface occludes the active sites, whereas in the PrTX-I structure they are exposed to solvent, (C) 1998 Elsevier B.V. Ltd. All rights reserved.

Amino acid sequence and crystal structure of BaP1, a metalloproteinase from Bothrops asper snake venom that exerts multiple tissue-damaging activities

BaP1 is a 22.7-kD P-I-type zinc-dependent metalloproteinase isolated from the venom of the snake Bothrops asper, a medically relevant species in Central America. This enzyme exerts multiple tissue-damaging activities, including hemorrhage, myonecrosis, dermonecrosis, blistering, and edema. BaP1 is a single chain of 202 amino acids that shows highest sequence identity with metalloproteinases isolated front the venoms of snakes of the subfamily Crotalinae. It has six Cys residues involved in three disulfide bridges (Cys 117-Cys 197, Cys 159-Cys 181, Cys 157-Cys 164). It has the consensus sequence H(142)E(143)XXH(146)XXGXXH(152), as well as the sequence C164I165M166, which characterize the metzincin superfamily of metalloproteinases. The active-site cleft separates a major subdomain (residues 1-152), comprising four a-helices and a five-stranded beta-sheet, from the minor subdomain, which is formed by a single a-helix and several loops. The catalytic zinc ion is coordinated by the N-epsilon2 nitrogen atoms of His 142, His 146, and His 152, in addition to a solvent water molecule, which in turn is bound to Glu 143. Several conserved residues contribute to the formation of the hydrophobic pocket, and Met 166 serves as a hydrophobic base for the active-site groups. Sequence and structural comparisons of hemorrhagic and nonhemorrhagic P-I metalloproteinases from snake venoms revealed differences in several regions. In particular, the loop comprising residues 153 to 176 has marked structural differences between metalloproteinases with very different hemorrhagic activities. Because this region lies in close proximity to the active-site microenvironment, it may influence the interaction of these enzymes with physiologically relevant substrates in the extracellular matrix.

Crystal Structure of Bucain, a Three-Fingered Toxin from the Venom of the Malayan Krait (Bungarus candidus)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural basis for branching-enzyme activity of glycoside hydrolase family 57: Structure and stability studies of a novel branching enzyme from the hyperthermophilic archaeon Thermococcus Kodakaraensis KOD1

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of hemoglobin from the maned wolf (Chrysocyon brachyurus) using synchrotron radiation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

On negative flows of the AKNS hierarchy and a class of deformations of a bihamiltonian structure of hydrodynamic type

A deformation parameter of a bihamiltonian structure of hydrodynamic type is shown to parametrize different extensions of the AKNS hierarchy to include negative flows. This construction establishes a purely algebraic link between, on the one hand, two realizations of the first negative flow of the AKNS model and, on the other, two-component generalizations of Camassa-Holmand Dym-type equations. The two-component generalizations of Camassa-Holm- and Dym-type equations can be obtained from the negative-order Hamiltonians constructed from the Lenard relations recursively applied on the Casimir of the first Poisson bracket of hydrodynamic type. The positive-order Hamiltonians, which follow froth the Lenard scheme applied on the Casimir of the second Poisson bracket of hydrodynamic type, are shown to coincide with the Hamiltonians of the AKNS model. The AKNS Hamiltonians give rise to charges conserved with respect to equations of motion of two-component Camassa-Holm- and two-component Dym-type equations.

Mechanism of Action and Relationship Between Structure and Biological Activity of Ctx-Ha: A New Ceratotoxin-like Peptide from Hypsiboas albopunctatus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of magnesium on structure and properties of LiNbO3 prepared from polymeric precursors

The effect of magnesium addition on the phase formation and electric properties of LiNbO3 powder prepared from polymeric precursor was analyzed. It was shown that the unit-cell volume of the rhombohedral phase decreased with increasing magnesium concentration. Small amounts of secondary phases were observed in LiNbO3 powder doped with 5 and 10 mol% Mg+2. These results indicated that the Mg+2 ion was substituted for niobium ion in the rhombohedral phase. The addition of Mg+2 promotes densification of LiNbO3 ceramics. It was noticed that the increase in additive concentration leads to a decrease of electric properties, K-p and d(33). This is due to formation of LiNb3O8 and MgNb2O6 phases at the grain boundaries. (C) 2002 Elsevier B.V. Ltd and Techna S.r.l. All rights reserved.

Structure and absolute configuration of a secolignan from Peperomia blanda

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Population structure of two Astyanax Baird & Girard, 1854 (Teleostei, Characidae) species from upper Paraguaçu river

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Leaf heliotropism in Styrax camporum Pohl from the Brazilian cerrado: distinct gas exchange and leaf structure, but similar leaf temperature and water relations

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biological Activity of Quinoline Alkaloids from Raulinoa echinata and X-ray Structure of Flindersiamine

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crystal structure of myotoxin-II: A myotoxic phospholipase A2 - Homologue from Bothrops moojeni venom.

The crystal structure of Myotoxin-II (MjTX-II), a Lys49 PLA(2)-homologue from Bothrops moojeni venom has been determined and refined at 2.0 Angstrom to a crystallographic residual of 19.7% (R-free = 28.1%). MjTX-II is a dimer in the crystal, with the monomers in the asymmetric unit related by a two-fold symmetry axis running through the dimer interface. The dimers of MjTX-II and the Lys49 PLA(2) from B. asper venom are similar, however the relative orientations of the monomers suggests a flexible dimer interface, which serves as a hinge between the two molecules.