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L D Possani

Publications and source records attributed to L D Possani.

138 records · Page 8Linked to original sources
PubMed1979

Comparison of phospholipase activity with direct and indirect lytic effects of animal venoms upon human red cells.

1. The venoms of 22 species of arthropods, saurians, elapids and crotalids were studied concerning the phospholipase activity and the presence of a direct and an indirect lytic effect upon human red cells. 2. The venoms from the spiders Latrodectus and "tarantula", and the venoms from the scorpions of the genus Centruroides are not haemolytic and do not have phospholipase activity. 3. Only the venoms of Apis mellifera and Naja naja siamensis have shown direct lytic effect. 4. All other venoms studied have an indirect haemolytic effect associated to a phospholipase activity, but there is indication that other agents might be implicated in the haemolytic processes.

Animals↗
PubMedDate not supplied

Synthesis and expression of the gene coding for noxiustoxin, a K+ channel-blocking peptide from the venom of the scorpion Centruroides noxius.

A set of six synthetic overlapping oligonucleotides coding for noxiustoxin were coupled into a continuous DNA fragment by means of recursive polymerase chain reaction. The polymerase chain reaction product was digested with SalI and HindIII, ligated into the E, coli vector pCSP 105 and expressed as a fusion protein. The fusion protein was purified and digested with trypsin and the hydrolysis products were separated by high-performance liquid chromatography. Approximately 1.3 mg of recombinant noxiustoxin per liter of culture was obtained. Amino acid analysis and N-terminal amino acid sequence of the recombinant noxiustoxin confirmed the nucleotide sequence of the cloned DNA. Binding experiments using rat brain synaptosomal membranes revealed that recombinant noxiustoxin displaced bound radioactive native NTX with a similar efficiency to cold native noxiustoxin.

Amino Acid Sequence↗
PubMedDate not supplied

Peptides and genes coding for scorpion toxins that affect ion-channels.

Most scorpion toxins are ligand peptides that recognize and bind to integral membrane proteins known as ion-channels. To date there are at least 202 distinct sequences described, obtained from 30 different species of scorpions, 27 from the family Buthidae and three from the family Scorpionidae. Toxins that recognize potassium and chloride channels are usually from 29 to 41 amino acids long, stabilized by three or four disulfide bridges, whereas those that recognize sodium channels are longer, 60 to 76 amino acid residues, compacted by four disulfide bridges. Toxins specific for calcium channels are scarcely known and have variable amino acid lengths. The entire repertoire of toxins, independently of their specificity, was analyzed together by computational programs and a phylogenetic tree was built showing two separate branches. The K(+) and Cl(-) channel specific toxins are clustered into 14 subfamilies, whereas those of Na(+) and Ca(2+) specific toxins comprise at least 12 subfamilies. There are clear similarities among them, both in terms of primary sequence and the main three-dimensional folding pattern. A dense core formed by a short alpha helix segment and several antiparallel beta-sheet stretches, maintained by disulfide pairing, seems to be a common structural feature present in all toxins. The physiological function of these peptides is manifested by a blockage of ion passage through the channels or by a modification of the gating mechanism that controls opening and closing of the ion pore.

Amino Acid Sequence↗