Photoaffinity labeling of scorpion toxin receptors associated with insect synaptosomal Na+ channels

Photoreactive and radioiodinated derivatives of several scorpion toxins acting on insect Na+ channels were prepared without loss of their pharmacological activities. Photoaffinity experiments were carried out on a synaptosomal fraction from the nerve cord of the cockroach Periplaneta americana: with all toxin derivatives, a single specifically labeled band was obtained with a molecular weight of 188,000 +/- 12,000 (n = 17). These results indicate for the first time the molecular weight of the scorpion toxin receptor from the insect nervous system which is probably associated with voltage sensitive Na+ channels. One of these toxins, toxin VII from Tityus serrulatus venom, has been previously shown to be active both in mammals and in insects, in rat brain synaptosomes this toxin labeled a Mr = 31,000 +/- 4,000 band in contrast, to observations in the insect preparation.     

Binding of Bacillus thuringiensis Cry1 Toxins to the Midgut Brush Border Membrane Vesicles of Chilo suppressalis (Lepidoptera: Pyralidae): Evidence of Shared Binding Sites

Binding and competition among Cry1Aa, Cry1Ac, and Cry1Ba toxins were analyzed quantitatively in vitro by using (sup125)I-labeled activated toxins and brush border membrane vesicles isolated from Chilo suppressalis larval midguts. The three toxins bound specifically to the midgut brush border membrane vesicles. Direct binding experiments showed that Cry1Aa and Cry1Ba recognized a single class of binding sites with different affinities, whereas Cry1Aa recognized two classes of binding sites, one with a high affinity and a low concentration and the other with a lower affinity but higher concentration. Competition experiments showed that toxins Cry1Ac and Cry1Ba shared a binding site in the C. suppressalis midgut membranes and that this site was also the low-affinity binding site for Cry1Aa.     

Biology and myriapod egg predation by the Neotropical myrmicine antStegomyrmex vizottoi (Hymenoptera: Formicidae)

Summary For the first time for a Neotropical ant and for Myrmicinae, the searching behavior and specialized predation of spirobolid millipede eggs byStegomyrmex vizottoi Diniz will be described. The relationship between morphology and habits is studied, as are nest architecture and distribution of the ant population in the nest chambers. We also report on some observations of behavior in the field and laboratory.We dedicate this paper to William L. Brown Junior, on the occasion of his 70^th birthday.     

Amino acid sequence of toxin VII,A β-toxin from the venom of the scorpton Tityus serrulatus

The sequence of the 61 amino acids of toxin VII, a β-toxin from the venom of the South American scorpion Tityus serrulatus, has been determined by automatic sequencing of the reduced and S-[¹⁴C] car?ymethylated protein and of tryptic peptides obtained before or after citraconylation of this protein. This toxin, the most active β-toxin from this venom, is the first Tityus toxin to be fully sequenced. The results clearly show that toxin VII belongs to the structural group of scorpion toxins originating from Central and North America.     

Bioreactor production of 2,3-butanediol by Pantoea agglomerans using soybean hull acid hydrolysate as substrate

Production of 2,3-butanediol (2,3-BD) by Pantoea agglomerans strain BL1 was investigated using soybean hull hydrolysate as substrate in batch reactors. The cultivation media consisted of a mixture of xylose, arabinose, and glucose, obtained from the hemicellulosic fraction of the soybean hull biomass. We evaluated the influence of oxygen supply, pH control, and media supplementation on the growth kinetics of the microorganism and on 2,3-BD production. P. agglomerans BL1 was able to simultaneously metabolize all three monosaccharides present in the broth, with average conversions of 75% after 48 h of cultivation. The influence of aeration conditions employed demonstrated the mixed acid pathway of 2,3-BD formation by enterobacteria. Under fully aerated conditions (2 vvm of air), up to 14.02 g L⁻¹ of 2.3-BD in 12 h of cultivation were produced, corresponding to yields of 0.53 g g⁻¹ and a productivity of 1.17 g L⁻¹ h⁻¹, the best results achieved. These results suggest the production potential of 2,3-BD by P. agglomerans BL1, which has been recently isolated from an environmental consortium. The present work proposes a solution for the usage of the hemicellulosic fraction of agroindustry biomasses, carbohydrates whose utilization are not commonly addressed in bioprocess.

     

A safe haven for potential reproductive aggregations of the critically endangered Brazilian guitarfish (Pseudobatos horkelii)

Brazilian endemic batoid elasmobranch populations have declined dramatically in the past 40 years due to anthropic activities (e.g., overfishing). The Brazilian guitarfish, Pseudobatos horkelii, included in the IUCN red list of endangered species [Critically Endangered (CR)], has been captured as by-catch by trawling fishing boats to the edge of extinction. Despite governmental conservation initiatives, the species is still caught and commercialized along the Brazilian coast. In this study, the authors report three rare aggregation events for the Brazilian coast of P. horkelii, inside the only nearshore no-entry Brazilian marine protected area. Strategies for its protection are also discussed.     

Polyglutamylase activity of tubulin tyrosine ligase-like 4 is negatively regulated by the never in mitosis gene A family kinase never in mitosis gene A -related kinase 5

BACKGROUNDTubulins, building blocks of microtubules, are modified substrates of diverse post-translational modifications including phosphorylation, polyglycylation and polyglutamylation. Polyglutamylation of microtubules, catalyzed by enzymes from the tubulin tyrosine ligase-like (TTLL) family, can regulate interactions with molecular motors and other proteins. Due to the diversity and functional importance of microtubule modifications, strict control of the TTLL enzymes has been suggested.AIMTo characterize the interaction between never in mitosis gene A-related kinase 5 (NEK5) and TTLL4 proteins and the effects of TTLL4 phosphorylation.METHODSThe interaction between NEK5 and TTLL4 was identified by yeast two-hybrid screening using the C-terminus of NEK5 (a.a. 260–708) as bait and confirmed by immunoprecipitation. The phosphorylation sites of TTLL4 were identified by mass spectrometry and point mutations were introduced.RESULTSHere, we show that NEK5 interacts with TTLL4 and regulates its polyglutamylation activity. We further show that NEK5 can also interact with TTLL5 and TTLL7. The silencing of NEK5 increases the levels of polyglutamylation of proteins by increasing the activity of TTLL4. The same effects were observed after the expression of the catalytically inactive form of NEK5. This regulation of TTLL4 activity involves its phosphorylation at Y815 and S1136 amino acid residues.CONCLUSIONOur results demonstrate, for the first time, the regulation of TTLL activity through phosphorylation, pointing to NEK5 as a potential effector kinase. We also suggest a general control of tubulin polyglutamylation through NEK family members in human cells.