BackgroundThe yellow fever mosquito, Aedes aegypti, is the primary vector for the viruses that cause yellow fever, mostly in tropical regions of Africa and in parts of South America, and human dengue, which infects 100 million people yearly in the tropics and subtropics. A better understanding of the structural biology of olfactory proteins may pave the way for the development of environmentally-friendly mosquito attractants and repellents, which may ultimately contribute to reduction of mosquito biting and disease transmission.MethodologyPreviously, we isolated and cloned a major, female-enriched odorant-binding protein (OBP) from the yellow fever mosquito, AaegOBP1, which was later inadvertently renamed AaegOBP39. We prepared recombinant samples of AaegOBP1 by using an expression system that allows proper formation of disulfide bridges and generates functional OBPs, which are indistinguishable from native OBPs. We crystallized AaegOBP1 and determined its three-dimensional structure at 1.85 Å resolution by molecular replacement based on the structure of the malaria mosquito OBP, AgamOBP1, the only mosquito OBP structure known to date.ConclusionThe structure of AaegOBP1 ( = AaegOBP39) shares the common fold of insect OBPs with six α-helices knitted by three disulfide bonds. A long molecule of polyethylene glycol (PEG) was built into the electron-density maps identified in a long tunnel formed by a crystallographic dimer of AaegOBP1. Circular dichroism analysis indicated that delipidated AaegOBP1 undergoes a pH-dependent conformational change, which may lead to release of odorant at low pH (as in the environment in the vicinity of odorant receptors). A C-terminal loop covers the binding cavity and this “lid” may be opened by disruption of an array of acid-labile hydrogen bonds thus explaining reduced or no binding affinity at low pH.

Glyoxalase II is a hydrolytic enzyme part of the glyoxalase system, responsible for detoxifying several cytotoxic compounds employing glutathione. Glyoxalase II belongs to the superfamily of metallo-beta-lactamases, with a conserved motif able to bind up to two metal ions in their active sites, generally zinc. Instead, several eukaryotic glyoxalases II have been characterized with different ratios of iron, zinc, and manganese ions. We have expressed a gene coding for a putative member of this enzyme superfamily from Salmonella typhimurium that we demonstrate, on the basis of its activity, to be a glyoxalase II, named GloB. Recombinant GloB expressed in Escherichia coli was purified with variable amounts of iron, zinc, and manganese. All forms display similar activities, as can be shown from protein expression in minimal medium supplemented with specific metal ions. The crystal structure of GloB solved at 1.4 A shows a protein fold and active site similar to those of its eukaryotic homologues. NMR and EPR experiments also reveal a conserved electronic structure at the metal site. GloB is therefore able to accommodate these different metal ions and to carry out the hydrolytic reaction with similar efficiencies in all cases. The metal promiscuity of this enzyme (in contrast to other members of the same superfamily) can be accounted for by the presence of a conserved Asp residue acting as a second-shell ligand that is expected to increase the hardness of the metal binding site, therefore favoring iron uptake in glyoxalases II.

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Triose phosphate isomerase (TIM) is responsible for the interconversion between GAP and DHAP in the glycolytic pathway. Two crystal forms belonging to space group P2 1 2 1 2 1 were obtained by the hanging-drop method and were designated A and B. Synchrotron X-ray diffraction data were collected for both forms. Form A had unit-cell parameters a = 65.14, b = 72.45, c = 93.24 A Ê and diffracted to 2.25 A Ê at 85 K, whereas form B had unit-cell parameters a = 73.02, b = 79.80, c = 172.85 A Ê and diffracted to 2.85 A Ê at room temperature. Molecular replacement was employed to solve the structures, using human TIM as a search model. Further re®nement of both structures is under way and is expected to shed light on the recently reported conformational studies for rabbit TIM.

Vamos, não chores. A infância está perdida. A mocidade está perdida. Mas a vida não se perdeu. O primeiro amor passou. O segundo amor passou. O terceiro amor passou. Mas o coração continua. Perdeste o melhor amigo. Não tentaste qualquer viagem. Não possuis carro, navio, terra. Mas tens um cão. Algumas palavras duras, em voz mansa, te golpearam. Nunca, nunca cicatrizam. Mas, e o humour? A injustiça não se resolve. À sombra do mundo errado murmuraste um protesto tímido. Mas virão outros. Tudo somado, devias precipitar-te, de vez, nas águas. Estás nu na areia, no vento... Dorme, meu filho.

a b s t r a c tXylella fastidiosa is responsible for a wide range of economically important plant diseases. We report here the crystal structure and kinetic data of Xylellain, the first cysteine protease characterized from the genome of the pathogenic X. fastidiosa strain 9a5c. Xylellain has a papain-family fold, and part of the N-terminal sequence blocks the enzyme active site, thereby mediating protein activity. One novel feature identified in the structure is the presence of a ribonucleotide bound outside the active site. We show that this ribonucleotide plays an important regulatory role in Xylellain enzyme kinetics, possibly functioning as a physiological mediator. Structured summary of protein interactions:Xylellain and Xylellain bind by X-ray crystallography (View interaction)

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