Common evolution of waprin and kunitz-like toxin families in Australian venomous snakes

The venoms of Australian snakes contain a myriad of pharmacologically active toxin components. This study describes the identification and comparative analysis of two distinct toxin families, the kunitztype serine protease inhibitors and waprins, and demonstrates a previously unknown evolutionary link between the two. Multiple cDNA and full-length gene isoforms were cloned and shown to be composed of three exons separated by two introns. A high degree of identity was observed solely within the first exon which coded for the propeptide sequence and its cleavage site, and indicates that each toxin family has arisen from a gene duplication event followed by diversification only within the portion of the gene coding for the functional toxin. It is proposed that while the mechanism of toxin secretion is highly conserved, diversification of mature toxin sequences allows for the existence of multiple protein isoforms in the venom to adapt to variations within the prey environment.

Distinct activities of novel neurotoxins from Australian venomous snakes for nicotinic acetylcholine receptors

Envenomation from Australian elapid snakes results in a myriad of neurological effects due to post-synaptic neurotoxins that bind and inhibit nicotinic acetylcholine receptors (nAChRs) of neurons and muscle fibres. However, despite the significant physiological effects of these toxins, they have remained largely undercharacterised at the molecular level. This study describes the identification and comparative analysis of multiple neurotoxin isoforms from ten Australian snakes, including functional characterisation of two of these isoforms, Os SNTX-1 from Oxyuranus scutellatus and the more potent Pt LNTX-1 from Pseudonaja textilis. Electrophysiological recordings from adrenal chromaffin cells demonstrate that both neurotoxins act as competitive antagonists of nAChRs in a concentration-dependent manner. Their effects upon spontaneous and nerve-evoked membrane responses at the amphibian neuromuscular junction provide further evidence that both toxins bind muscle nAChRs in an irreversible manner. This study represents one of the most comprehensive descriptions to date of the sequences and activity of individual Australian elapid neurotoxins.

Identification and analysis of venom gland-specific genes from the coastal taipan (Oxyuranus scutellatus) and related species

Australian terrestrial elapid snakes contain amongst the most potently toxic venoms known. However, despite the well-documented clinical effects of snake bite, little research has focussed on individual venom components at the molecular level. To further characterise the components of Australian elapid venoms, a complementary (cDNA) microarray was produced from the venom gland of the coastal taipan (Oxyuranus scutellatus) and subsequently screened for venom gland-specific transcripts. A number of putative toxin genes were identified, including neurotoxins, phospholipases, a pseudechetoxin-like gene, a venom natriuretic peptide and a nerve growth factor together with other genes involved in cellular maintenance. Venom gland-specific components also included a calglandulin-like protein implicated in the secretion of toxins from the gland into the venom. These toxin transcripts were subsequently identified in seven other related snake species, producing a detailed comparative analysis at the cDNA and protein levels. This study represents the most detailed description to date of the cloning and characterisation of different genes associated with envenomation from Australian snakes.

Inhibitors of V-type ATPases, bafilomycin A1 and concanamycin A, protect against beta-amyloid-mediated effects on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction

The functional viability of cells can be evaluated using a number of different assay determinants. One common assay involves exposing cells to 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), which is converted intracellularly to a colored formazan precipitate and often used to assess amyloid peptide-induced cytotoxic effects. The MTT assay was employed to evaluate the role of endosomal uptake and lysosomal acidification in amyloid peptide-treated differentiated PC12 cell cultures using selective vacuolar-type (V-type) ATPase inhibitors. The macrolides bafilomycin A1 (BAF) and concanamycin A (CON) block lysosomal acidification through selective inhibition of the V-type ATPase. Treating nerve growth factor-differentiated PC12 cells with nanomolar concentrations of BAF or CON provides complete protection against the effects of beta-amyloid peptides Abeta(1-42), Abeta(1-40), and Abeta(25-35) and of amylin on MTT dye conversion. These macrolides do not inhibit peptide aggregation, act as antioxidants, or inhibit Abeta uptake by cells. Measurements of lysosomal acidification reveal that the concentrations of BAF and CON effective in reversing Abeta-mediated MTT dye conversion also reverse lysosomal pH. These results suggest that lysosomal acidification is necessary for Abeta effects on MTT dye conversion.

Geophysical variables and behavior: LXXXIV. Quantitative increases in group aggression in male epileptic rats during increases in geomagnetic activity

Over a 24-day period the magnitude of the average, 24 hr., global geomagnetic activity was significantly correlated (r and rho about .40) with the average numbers of agonistic (biting) responses between midnight and 0100 hr. in a group of four males epileptic rats. Geomagnetic activity was not significantly correlated with quantitative measures of boxing, mounting, eating, grooming, or drinking. Partial correlations, which also controlled for a weak serial correlation, indicated that the index of geomagnetic activity was only associated with the biting (partial r = .54) behaviors. The results replicated previous studies and suggest that the relationship between aggression and geomagnetic activity is specific and not an artifact of a generalized increase in multiple domains of behavior.

The alpha subunit of RNA polymerase and transcription antitermination

The N gene product of coliphage gamma, with a number of host proteins (Nus factors), regulates phage gene expression by modifying RNA polymerase to a form that overrides transcription-termination signals. Mutations in host nus genes diminish this N-mediated antitermination. Here, we report the isolation and characterization of the rpoAD305E mutation, a single amino acid change in the carboxy terminal domain (CTD) of the alpha subunit of RNA polymerase, that enhances N-mediated antitermination. A deletion of the 3' terminus of rpoA, resulting in the expression of an alpha subunit missing the CTD, also enhances N-mediated antitermination and, similar to rpoAD305E, suppresses the effect of nus mutations. Thus, the N-Nus complex may be affected through contacts with the CTD of the alpha subunit of RNA polymerase, as is a group of regulatory proteins that influences initiation of transcription. What distinguishes our findings on the N-Nus complex from those of previous studies with transcription proteins is that all of the regulators characterized in those studies bind DNA and influence transcription initiation; whereas the N-Nus complex binds RNA and affects transcription elongation. A screen of some previously identified rpoA mutations that influence transcription activators revealed only one other amino acid change, L290H, in the CTD of the alpha subunit, that influences antitermination. Although our results provide evidence that interactions of the alpha subunit of RNA polymerase must be considered in forming models of transcription antitermination, they do not provide information as to whether the interactions of alpha that ultimately influence antitermination occur during initiation or during elongation of transcription.