The flexible nature of a critical peptide region common to all Elapidae "short" neurotoxins

Snake venom cardiotoxins-structure, dynamics, function and folding

Snake cardiotoxins are highly basic (pI > 10) small molecular weight (approximately 6.5 kDa), all beta-sheet proteins. They exhibit a broad spectrum of interesting biological activities. The secondary structural elements in these toxins include antiparallel double and triple stranded beta-sheets. The three dimensional structures of these toxins reveal an unique asymmetric distribution of the hydrophobic and hydrophilic amino acids. The 3D structures of closely related snake venom toxins such as neurotoxins and cardiotoxin-like basic proteins (CLBP) fail to show similar pattern(s) in the distribution of polar and nonpolar residues. Recently, many novel biological activities have been reported for cardiotoxins. However, to-date, there is no clear structure-function correlation(s) available for snake venom cardiotoxins. The aim of this comprehensive review is to summarize and critically evaluate the progress in research on the structure, dynamics, function and folding aspects of snake venom cardiotoxins.

Conformational properties of the neurotoxins and cytotoxins isolated from Elapid snake venoms

The review will critically assess the information available on the conformation of homologous neurotoxins and cytotoxins isolated from Elapid snakes. Particular attention will be given to the dynamics of the molecules in solution because there is the possibility that defined intramolecular rearrangements are involved at the sites of action. Such properties will be then reconciled with the known X-ray crystallographic and sequence data in order to derive likely structure-activity relationships.

Molecular dynamics of two homologous neurotoxins revealed by 1H-2H exchange: an infrared spectrometry study

Temperature effects on the hydrogen exchange kinetics and the infrared spectra of two homologous snake neurotoxins (Laticauda semifasciata erabutoxin b and Naja nigricollis toxin alpha) were investigated between 10 and 40 degrees C, at their isoionic pH. (1) Erabutoxin b is more accessible to the solvent than toxin alpha. (2) With increasing temperature, both toxin molecules undergo a global transition affecting the most accessible as well as the most buried hydrogens: the overall accessibility changes are more important for erabutoxin b than for toxin alpha. The different conformational stabilities of the toxins are also qualitatively supported by the temperature-induced shifts which affect the infrared amide I band of toxin alpha only. The existence of two conformer families could be responsible for the different conformational stability of these proteins.

Circular dichroism of elapidae protein toxins

The effect of temperature variation on the circular dichroic spectra of four Elapid snake toxins (one short neurotoxin, two long neurotoxins and one cytotoxin) was determined and the results compared. The three neurotoxins have in common a delicately balanced conformation which can be perturbed independently of the predominant secondary structuring. Despite the many differences in sequence between long and short neurotoxins, the nature of this balance seems to be the same in both types and it is considered to involve an equilibrium between two defined conformers. Such properties could not be discerned in the cytotoxin studied, but related work suggests that they could nevertheless be present in some cases. In terms of global structure, long neurotoxins may have a greater proportion of 'random chain' inherent than short neurotoxins, the latter having extensive beta-sheet. The important feature of all toxins is deemed to be a conformational freedom defined by the secondary structuring and characteristic disulphide bridge formation. Possible relevance to toxicity of such a property is discussed.