Cold adaptation in DEAD-box proteins.

Spontaneous rearrangements of RNA structures are usually characterized by large activation energies and thus become very slow at low temperatures, yet RNA structure must remain dynamic even in cold-adapted (psychrophilic) organisms. DEAD-box proteins constitute a ubiquitous family of RNA-dependent ATPases that can often unwind short RNA duplexes in vitro (helicase activity), hence the belief that one of their major (though not exclusive) roles in vivo is to assist in RNA rearrangements. Here, we compare two Escherichia coli DEAD-box proteins and their orthologs from the psychrophilic bacteria Pseudoalteromonas haloplanktis and Colwellia psychrerythraea from the point of view of enzymatic properties.

Using dried blood spots stored on filter paper to measure cholinesterase activity in wild avian species.

Birds of prey that are poisoned by cholinesterase inhibitors (e.g. organophosphate and carbamate insecticides) are often cared for at animal shelters, rehabilitation centres and wildlife diagnostic facilities.

N-caffeoylphenalkylamide derivatives as bacterial efflux pump inhibitors.

As part of an ongoing project to identify plant natural products as efflux pump inhibitors (EPIs), bioassay-guided fractionation of the methanolic extract of Mirabilis jalapa Linn. (Nyctaginaceae) led to the isolation of an active polyphenolic amide: N-trans-feruloyl 4'-O-methyldopamine. This compound showed moderate activity as an EPI against multidrug-resistant (MDR) Staphylococcus aureus overexpressing the multidrug efflux transporter NorA, causing an 8-fold reduction of norfloxacin MIC at 292 microM (100 microg/mL).

Determinants of potency on alpha-conotoxin MII, a peptide antagonist of neuronal nicotinic receptors.

Alpha-conotoxin MII, a peptide toxin isolated from Conus magus, antagonizes a subset of neuronal nicotinic receptors. Rat alpha3beta2 receptors, expressed in Xenopus oocytes, are blocked with an IC(50) of 3.7 +/- 0.

Antioxidant flavonoids and phenolic acids from leaves of Leea guineense G Don (Leeaceae).

From leaves of Leea guineense (Leeaceae) three hydrophilic flavonoids were isolated and identified as quercetin-3'-sulphate-3-O-alpha-L-rhamnopyranoside, quercetin-3,3'-disulphate and a new flavonoid sulphate, quercetin-3,3',4'-trisulphate, together with kaempferol, quercetin, quercitrin, mearnsitrin, gallic acid and ethyl gallate. The structures were established by spectroscopic analysis (UV, MS, (1)H-NMR, (13)C-NMR and 2D-NMR). Their antioxidant effect on free radical scavenging was evaluated in the DPPH assay.

Venomous cone snails: molecular phylogeny and the generation of toxin diversity.

In order to investigate the generation of conotoxin diversity, delta-conotoxin sequences from nine Conus species were analyzed in the context of their phylogeny. Using a standard molecular marker, mitochondrial 16S RNA, we determined that the delta-conotoxins were derived from three distinct species clades based on the phylogenetic reconstruction of a large set (>80) of Conus species and other toxoglossate molluscs. Four different mechanisms appear to have contributed to the diversity of the delta-conotoxins analyzed: (1) Speciation: Delta-conotoxins in different species diverge from each other (the prepro regions of orthologous genes somewhat more slowly than the reference rRNA rate, the mature toxin regions significantly faster).

Single-residue alteration in alpha-conotoxin PnIA switches its nAChR subtype selectivity.

alpha-Conotoxins are disulfide-rich peptides that are competitive antagonists of nicotinic acetylcholine receptors (nAChRs). Despite their small size, different alpha-conotoxins are able to discriminate among different subtypes of mammalian nAChRs. In this report, the activity of two peptides from the venom of Conus pennaceus, alpha-conotoxins PnIA and PnIB, are examined.

Speciation of cone snails and interspecific hyperdivergence of their venom peptides. Potential evolutionary significance of introns.

All 500 species of cone snails (Conus) are venomous predators. From a biochemical/genetic perspective, differences among Conus species may be based on the 50-200 different peptides in the venom of each species. Venom is used for prey capture as well as for interactions with predators and competitors.

alpha-conotoxin AuIB selectively blocks alpha3 beta4 nicotinic acetylcholine receptors and nicotine-evoked norepinephrine release.

Neuronal nicotinic acetylcholine receptors (nAChRs) with putative alpha3 beta4-subunits have been implicated in the mediation of signaling in various systems, including ganglionic transmission peripherally and nicotine-evoked neurotransmitter release centrally. However, progress in the characterization of these receptors has been hampered by a lack of alpha3 beta4-selective ligands. In this report, we describe the purification and characterization of an alpha3 beta4 nAChR antagonist, alpha-conotoxin AuIB, from the venom of the "court cone," Conus aulicus.

Differential targeting of nicotinic acetylcholine receptors by novel alphaA-conotoxins.

We describe the isolation and characterization of two peptide toxins from Conus ermineus venom targeted to nicotinic acetylcholine receptors (nAChRs). The peptide structures have been confirmed by mass spectrometry and chemical synthesis. In contrast to the 12-18 residue, 4 Cys-containing alpha-conotoxins, the new toxins have 30 residues and 6 Cys residues.

A noncompetitive peptide inhibitor of the nicotinic acetylcholine receptor from Conus purpurascens venom.

A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist.

Determinants of specificity for alpha-conotoxin MII on alpha3beta2 neuronal nicotinic receptors.

The competitive antagonist alpha-conotoxin-MII (alpha-CTx-MII) is highly selective for the alpha3beta2 neuronal nicotinic receptor. Other receptor subunit combinations (alpha2beta2, alpha4beta2, alpha3beta4) are >200-fold less sensitive to blockade by this toxin. Using chimeric and mutant subunits, we identified amino acid residues of alpha3 and beta2 that participate in determination of alpha-CTx-MII sensitivity.

A new alpha-conotoxin which targets alpha3beta2 nicotinic acetylcholine receptors.

We have isolated a 16-amino acid peptide from the venom of the marine snail Conus magus which potently blocks nicotinic acetylcholine receptors (nAChRs) composed of alpha3beta2 subunits. This peptide, named alpha-conotoxin MII, was identified by electrophysiologically screening venom fractions against cloned nicotinic receptors expressed in Xenopus oocytes. The peptide's structure, which has been confirmed by mass spectrometry and total chemical synthesis, differs significantly from those of all previously isolated alpha-conotoxins.