Structure,function and evolution of the hemerythrin‐like domain superfamily

Hemerythrin‐like proteins have generally been studied for their ability to reversibly bind oxygen through their binuclear nonheme iron centers. However, in recent years, it has become increasingly evident that some members of the hemerythrin‐like superfamily also participate in many other biological processes. For instance, the binuclear nonheme iron site of YtfE, a hemerythrin‐like protein involved in the repair of iron centers in Escherichia coli, catalyzes the reduction of nitric oxide to nitrous oxide, and the human F‐box/LRR‐repeat protein 5, which contains a hemerythrin‐like domain, is involved in intracellular iron homeostasis. Furthermore, structural data on hemerythrin‐like domains from two proteins of unknown function, PF0695 from Pyrococcus furiosus and NMB1532 from Neisseria meningitidis, show that the cation‐binding sites, typical of hemerythrin, can be absent or be occupied by metal ions other than iron. To systematically investigate this functional and structural diversity of the hemerythrin‐like superfamily, we have collected hemerythrin‐like sequences from a database comprising fully sequenced proteomes and generated a cluster map based on their all‐against‐all pairwise sequence similarity. Our results show that the hemerythrin‐like superfamily comprises a large number of protein families which can be classified into three broad groups on the basis of their cation‐coordinating residues: (a) signal‐transduction and oxygen‐carrier hemerythrins (H‐HxxxE‐HxxxH‐HxxxxD); (b) hemerythrin‐like (H‐HxxxE‐H‐HxxxE); and, (c) metazoan F‐box proteins (H‐HExxE‐H‐HxxxE). Interestingly, all but two hemerythrin‐like families exhibit internal sequence and structural symmetry, suggesting that a duplication event may have led to the origin of the hemerythrin domain.     

Complement Proteins Are Present in Developing Endochondral Bone and May Mediate Cartilage Cell Death and Vascularization

Normal endochondral bone formation follows a temporal sequence: immature or resting chondrocytes move away from the resting zone, proliferate, flatten, become arranged into columns, and finally become hypertrophic, disintegrate, and are replaced by bone. The mechanisms that guide this process are incompletely understood, but they include programmed cell death, a stage important in development and some disease processes. Using immunofluorescence we have studied the distribution of various complement proteins to examine the hypothesis that this sequence of events, particularly cell disintegration and matrix dissolution, are complement mediated. The results of these studies show that complement proteins C3 and Factor B are distributed uniformly in the resting and proliferating zones. Properdin is localized in the resting and hypertrophic zone but not in the proliferating zone. Complement proteins C5 and C9 are localized exclusively in the hypertrophic zones. This anatomically segregated pattern of distribution suggests that complement proteins may be important in cartilage–bone transformation and that the alternate pathway is involved.     

Inhibition of plant cytokinesis by deoxyguanosine and caffeine

The efficacy of 2′-deoxyguanosine (GdR) on the induction of binucleate cells in onion root tips was studied. GdR inhibits plant cytokinesis during the last part of the mitotic period. Apparently, this deoxynucleoside causes a considerable slowing down in the mitotic rate (50%) and also has a slight effect as an inhibitor of cytokinesis (30%). The effect on the mitotic rate was established with 1 mM colchicine (metaphase rate) and with 5 mM caffeine (telophase rate). Since 1 mM GdR has a remarkable potentiating action on inhibition of cytokinesis by caffeine, we postulate that GdR, or a phosphorylated derivative from it, inhibits cytokinesis by a similar mechanism as caffeine. According to our postulation, GdR interferes with a certain ATPase activity required for membrane fusion of the Golgi vesicles during plant cytokinesis.     

Properties of a novel oligonucleotide-releasing bidirectional DNA exonuclease from mouse myeloma

Highly purified, but not homogeneous, samples of helix-destabilizing protein 1 from mouse myeloma contain a novel oligonucleotide-releasing DNA exonuclease. This enzyme was separated from helix-destabilizing protein 1 and obtained in highly purified form. A polypeptide of Mr 41 000 is a main constituent of the purified enzyme, and this polypeptide comigrated with the exonuclease activity during the final step of the purification, Sephacryl S-200 gel filtration where the enzyme had a native Mr of 40 000. Overall purification of enzyme activity was greater than 20 000-fold. This exonuclease releases 5'-oligonucleotides in a limited processive manner in both the 5'----3' and 3'----5' directions. Activity of the enzyme is resistant to 1 mM N-ethylmaleimide, requires a divalent cation, has an alkaline pH optimum, and degrades single-stranded DNA much faster than double-stranded DNA or RNA. The predominant oligonucleotide product with uniformly labeled substrates is (pdN)2. With 3' end labeled substrates, greater than 95% of the labeled products are (pdN)4 and (pdN)5; with 5' end labeled substrates, the main labeled product is (pdA)2. The rate of product release from 3' and 5' end labeled substrates is nearly identical at 37 degrees C. A model of the action of this enzyme and a comparison with a human placenta exonuclease [Doniger, J., & Grossman, L. (1976) J. Biol. Chem. 251, 4579-4587] are discussed.     

Seed dispersal distance,seed morphology,and recruitment in the Chilean sclerophyllous tree Quillaja saponaria: implications for passive restoration in a semiarid ecosystem

Recolonization of wind-dispersed tree species in degraded areas may decline with distance from remnant forest fragments because seed rain frequently decreases with distance from the seed source. However, regeneration of these species may be even more limited to sites close to the seed source if dispersal distance is negatively affected by seed mass, and germination probability is positively affected by seed mass. We evaluated these hypotheses in a Mediterranean-type ecosystem of central Chile, using the wind-dispersed tree species Quillaja saponaria. We assessed the seed rain curve in a degraded open area adjacent to a remnant forest fragment of this species, and related seed mass with dispersal distance from the seed source. Then, we evaluated the relationship between seed mass, germination, and seedling growth, and if seeds that fall nearer the seed source have greater germination probability. We found a decreasing seed rain with the distance from the seed source. Seed mass was not related to dispersal distance, although seeds with higher wing area dispersed further. Germination probability was significantly and positively related to the seed mass. We observed no significant relationship between distance and germination probability. We conclude that germination probability of this species does not vary along the seed rain curve, and that the recruitment density would be greater near the seed source only due to decreasing seed rain with distance. Our results suggest that this species has the potential to be passively restored in degraded areas, especially within the first 70 m from the remnant forest fragments.

     

Comparison of evoked vs. spontaneous tics in a patient with trigeminal neuralgia (tic doloureux)

A 53-year old woman with tic doloureaux, affecting her right maxillary division of the trigeminal nerve (V2), could elicit shooting pains by slightly tapping her teeth when off medication. The pains, which she normally rated as > 6/10 on a visual analog scale (VAS), were electric shock-like in nature. She had no other spontaneous or ongoing background pain affecting the region. Based on her ability to elicit these tics, functional magnetic resonance imaging (fMRI) was performed while she produced brief shocks every 2 minutes on cue (evoked pain) over a 20 min period. In addition, she had 1–2 spontaneous shocks manifested between these evoked pains over the course of functional image acquisition. Increased fMRI activation for both evoked and spontaneous tics was observed throughout cortical and subcortical structures commonly observed in experimental pain studies with healthy subjects; including the primary somatosensory cortex, insula, anterior cingulate, and thalamus. Spontaneous tics produced more decrease in signals in a number of regions including the posterior cingulate cortex and amygdala, suggesting that regions known to be involved in expectation/anticipation may have been activated for the evoked, but not spontaneous, tics. In this patient there were large increases in activation observed in the frontal regions, including the anterior cingulate cortex and the basal ganglia. Spontaneous tics showed increased activation in classic aversion circuitry that may contribute to increased levels of anxiety. We believe that this is the first report of functional imaging of brain changes in tic-doloureaux.     

High Throughput Discovery of Solar Fuels Photoanodes in the CuO–V2O5 System

Solar photoelectrochemical generation of fuel is a promising energy technology yet the lack of an efficient, robust photoanode remains a primary materials challenge in the development and deployment of solar fuels generators. Metal oxides comprise the most promising class of photoanode materials, but no known material meets the demanding requirements of low band gap energy, photoelectrocatalysis of the oxygen evolution reaction (OER), and stability under highly oxidizing conditions. Here, the identification of new photoelectroactive materials is reported through a strategic combination of combinatorial materials synthesis, high‐throughput photoelectrochemistry, optical spectroscopy, and detailed electronic structure calculations. Four photoelectrocatalyst phases, α ‐Cu₂V₂O₇, β ‐Cu₂V₂O_7, γ ‐Cu₃V₂O₈, and Cu₁₁V₆O₂₆, are reported with band gap energy at or below 2 eV. The photoelectrochemical properties and 30 min stability of these copper vanadate phases are demonstrated in three different aqueous electrolytes (pH 7, pH 9, and pH 13), with select combinations of phase and electrolyte exhibiting unprecedented photoelectrocatalytic stability for metal oxides with sub‐2 eV band gap. Through integration of experimental and theoretical techniques, new structure‐property relationships are determined and establish CuO–V₂O₅ as the most prominent composition system for OER photoelectrocatalysts, providing crucial information for materials genomes initiatives and paving the way for continued development of solar fuels photoanodes.     

In vitro activity of N-benzenesulfonylbenzotriazole on Trypanosoma cruzi epimastigote and trypomastigote forms

Chagas disease is still an important health problem in Central and South America. However, the only drugs currently available for specific treatment of this disease may induce toxic side effects in the host. The aim of this work was to determine the activity of N-benzenesulfonylbenzotriazole (BSBZT) against the protozoan parasite Trypanosoma cruzi. The effects of BSBZT and benzotriazole (BZT) were compared to those of benznidazole (BZL) on epimastigote and trypomastigote forms. BSBZT was found to have an in vitro growth inhibitory dose-dependent activity against epimastigotes, with flow cytometry analysis confirming that the treated parasites presented size reduction. BSBZT showed an IC(50) of 21.56 μg/mL (81.07 μM) against epimastigotes at 72 h of incubation, whereas BZT did not affect the growth of this parasite form. Furthermore, the toxic effect of BSBZT, was stronger and appeared earlier (at 24h) in trypomastigotes than in epimastigotes, with the LC(50) of this compound being 28.40 μg/mL (106.79 μM) against trypomastigotes. The concentrations of BSBZT used in this study presented low hemolytic activity and cytotoxicity. Consequently, at concentrations near IC(50) and LC(50) (25μg/mL), BSBZT caused only 2.4% hemolysis and 15% of RAW 264.7 cell cytotoxicity. These results reveal the potential of BSBZT as a prototype in drug design for developing new anti-T. cruzi compounds.