Consuelo Medina García

Oxidative refolding chromatography: folding of the scorpion toxin Cn5

We have made an immobilized and reusable molecular chaperone system for oxidative refolding chromatography. Its three components—GroEL minichaperone (191–345), which can prevent protein aggregation; DsbA, which catalyzes the shuffling and oxidative formation of disulfide bonds; and peptidyl–prolyl isomerase—were immobilized on an agarose gel. The gel was applied to the refolding of denatured and reduced scorpion toxin Cn5. The 66–residue toxin, which has four disulfide bridges and a cis peptidyl–proline bond, had not previously been refolded in reasonable yield. We recovered an 87% yield of protein with 100% biological activity.

Cloning and characterization of cDNAs that code for Na+ -channel-blocking toxins of the scorpion Centruroides noxius Hoffmann

With the purpose of studying the organization and characteristics of the genes that code for toxins present in the venom of the Mexican scorpion, Centruroides noxius Hoffmann (CnH), we prepared a lambda gt11 cDNA library from the venom glands. Using specific oligodeoxyribonucleotides (oligos) designed according to known amino acid (aa) sequences of CnH toxins (STox), we detected several positive clones, determined their nucleotide (nt) sequences and deduced their aa sequences. A comparative analysis of these sequences with previously reported STox revealed that CnH cDNAs code for a family of very similar STox. The cDNA coding for a known STox, II-10, was cloned. Additionally, three other complete (new) nt sequences were obtained for cDNAs encoding peptides similar to STox 1 from CnH or variants 2 and 3 from Centruroides sculpturatus Ewing. Southern blot genomic DNA analysis showed a minimum size of approximately 600 bp as EcoRI fragments for elements of this family. PCR amplifications of CnH genomic DNA and hybridization of PCR products with specific probes indicated that the genomic structural regions that code for these genes do not contain introns, or at least not large introns.

Isolation, Characterization and Comparison of a Novel Crustacean Toxin with a Mammalian Toxin from the Venom of the Scorpion Centruroides noxius Hoffmann

A novel crustacean-specific toxin, Cn5, containing 66 amino acid residues was isolated from the venom of the scorpion Centruroides noxius Hoffmann. It is stabilized by four disulfide bridges, formed between Cys12-Cys65, Cys16-Cys41, Cys25-Cys46 and Cys29-Cys48. Toxicity tests revealed that Cn5 is a toxin that affects arthropods but not mammals. However, at high concentrations, Cn5 does displace the mammal-specific toxin Cn2 from rat brain synaptosomes. The concentration of Cn5 that produces half-maximal inhibition (IC50) was estimated to be 100 microM. Sequence comparison of Cn5 with toxin Cn2, a mammal-specific toxin from the same scorpion, showed the presence of two sequence stretches, at positions 30 to 38 and 49 to 58, where the majority of the differences are concentrated. On the three-dimensional structure of Cn5 it is demonstrated that these two sequence stretches form a continuous surface region near the site thought to bind to the sodium channel. We assume that this region might be implicated in determining species specificity.

Cloning of Genes Encoding Scorpion Toxins: An Interpretative Review

AbstractScorpion toxins (Stox) are polypeptides intensively investigated because they are excellent models to study protein-structure-function relationships and exquisite tools to access ion channel functions. Recently, techniques of molecular biology have been used to clone the genes encoding toxins specific for Na+-channels. Genes from scorpions of the genus Androctonus, Centruroides, Leiurus, Tityus and Bothus have been cloned and their nucleotide (nt) sequence determined. Data from complementary DNA (cDNA) cloning of Stox from the genus before mentioned and genomic cloning of Stox genes from scorpions of the genus Tityus and Androctonus have provided information for the deduction of the structure of the transcriptional units encoding toxin genes of these scorpions. It seems that transcription of these genomic regions generates pre messenger RNAs (pre-mRNAs) of approximately 800nt containing an intron of approximately 470nt, located within the region encoding the signal peptide. The processing of these...

Analysis of the immune response induced by a scorpion venom sub-fraction, a pure peptide and a recombinant peptide, against toxin Cn2 of Centruroides noxius Hoffmann

Three different immunogens from the venom of the Mexican scorpion Centruroides noxius Hoffmann were used to study protective antibody response in mice and rabbits, challenged with toxin Cn2, one of the most abundant toxic peptide of this venom. The immunogens were: Cn5, a crustacean specific toxin; a recombinant protein containing the peptide Cn5 linked to the maltose transporter and a sub-fraction (F.II.5) containing 25 distinct peptides, among which is Cn5. Mice immunized with these three preparations, when directly challenged with Cn2 presented no apparent protection, whereas anti-sera produced in rabbits with these three immunogens were capable of partially neutralizing the effect of Cn2, when injected into naive mice. Cn5 rabbit anti-serum showed a better protective effect on mice, than the rabbit sera obtained against the two other antigens. The subcutaneous route of challenging mice was shown to be better than intraperitoneal injections. Comparative structural analysis of Cn5 with other toxins of this venom showed that our results are important to be taken into consideration, when choosing appropriate immunogens aimed at the production of better anti-venoms or for the rational design of possible vaccines.

SECLAVEMEX Aimed at Integrating Land-cover and Vegetation Mapping

Vegetation, either natural or cultural, from the local to global scale, portrays the baseline for land-use planning. In order to enhance the role of vegetation in land-use planning, distribution patterns in map formats need to be constructed.

Background on Vegetation Classification Systems

Vegetation is formed by plant species growing as the result of a long development process consistent with the places they inhabit and which constitutes a fundamental part of ecosystems. As a result, vegetation is understood as resulting from the effects of various environmental factors on sets of species which cohabit in a determined space and period (Velazquez and Romero 1999; FGDC 2005). Generally speaking, two major categories can be seen: cultural vegetation and natural vegetation. The former owes its development, permanence, and expression to processes regulated by the continuous activity of mankind, for example agricultural areas and planted forests, which are a relatively recent expression (to the order of decades and centuries). Natural vegetation, by contrast, is underlain by processes in the main determined by climatic, geomorphological, edaphic, and ecological components, which interact simultaneously and continuously over extended periods of time (to the order of hundreds to thousands of years). As the effects of human actions have become more evident, it has become increasingly difficult to determine the limits between natural and cultural vegetation, though international agreements exist which allow for the understanding of irrefutable predominance. Profound knowledge of vegetation in general, the directional forces determining its presence notwithstanding, is fundamental for multiple purposes as much locally as globally, particularly in terms of better vegetation management and conservation (Matteucci and Colma 1982; FGDC 2005).

The Inclusive Nature of SECLAVEMEX

The objective of this chapter was to return to the classification systems used across the whole of Mexico to illustrate explicitly the mechanics of affinity and compatibility between these various systems and SECLAVEMEX, retaining the strengths of previously proposed systems but resolving inconsistencies prevalent among them.

Proposal for a Standardized Hierarchical System for the Classification of Vegetation in Mexico

Classification sensu lato pursues the recognition of categories, the hierarchical arrangement expressing the (dis)similarity between them and the unique and distinct denominations between levels of division (Anonymous 2003). These principles have been applied across various disciplines related to biology, such as taxonomy, systematics, and phylogeny, which have taken on these tasks from a precise definition of the level of specific organization.