T-type Channels Become Highly Permeable to Sodium Ions Using an Alternative Extracellular Turret Region (S5-P) Outside the Selectivity Filter

T-type (Ca_v3) channels are categorized as calcium channels, but invertebrate ones can be highly sodium-selective channels. We illustrate that the snail LCa_v3 T-type channel becomes highly sodium-permeable through exon splicing of an extracellular turret and descending helix in domain II of the four-domain Ca_v3 channel. Highly sodium-permeable T-type channels are generated without altering the invariant ring of charged residues in the selectivity filter that governs calcium selectivity in calcium channels. The highly sodium-permeant T-type channel expresses in the brain and is the only splice isoform expressed in the snail heart. This unique splicing of turret residues offers T-type channels a capacity to serve as a pacemaking sodium current in the primitive heart and brain in lieu of Na_v1-type sodium channels and to substitute for voltage-gated sodium channels lacking in many invertebrates. T-type channels would also contribute substantially to sodium leak conductances at rest in invertebrates because of their large window currents.     

Expression in Escherichia coli of the death domain of the human p55 tumor necrosis factor receptor.

The p55 tumor necrosis factor receptor (TNF-RI) is the main receptor by which TNF exerts its effects. The signaling capacity largely depends on the presence of an intact C-terminal protein-protein interaction domain, a so-called death domain (DD). Here we report the expression and purification of the human TNF-RI DD as a fusion with the Escherichia coli thioredoxin A (TRX) protein. When expressed under control of the bacteriophage T7 promoter, TRX-DD accumulates as a soluble protein in the cytoplasm of E. coli. The TRX-DD protein was released from the cells into the periplasmic fraction after osmotic shock. Due to self-association of the DD, a large part of the material appeared as multimers; it could be removed by selective precipitation and a combination of ion-exchange and size-exclusion chromatography. This purification protocol yielded 30 mg of purified, monomeric protein from 1 liter of shake-flask culture. The purified TRX-DD was found to be functional as it still bound to the TNF-RI-associated DD protein and the intracellular part of TNF-RI. We conclude that TRX-DD is correctly folded and can be used for further structure/function analysis.     

Genomic medicine and neurological disease

“Genomic medicine” refers to the diagnosis, optimized management, and treatment of disease—as well as screening, counseling, and disease gene identification—in the context of information provided by an individual patient’s personal genome. Genomic medicine, to some extent synonymous with “personalized medicine,” has been made possible by recent advances in genome technologies. Genomic medicine represents a new approach to health care and disease management that attempts to optimize the care of a patient based upon information gleaned from his or her personal genome sequence. In this review, we describe recent progress in genomic medicine as it relates to neurological disease. Many neurological disorders either segregate as Mendelian phenotypes or occur sporadically in association with a new mutation in a single gene. Heritability also contributes to other neurological conditions that appear to exhibit more complex genetics. In addition to discussing current knowledge in this field, we offer suggestions for maximizing the utility of genomic information in clinical practice as the field of genomic medicine unfolds.     

Crystals and a low resolution structure of interleukin-2

Recombinant derived human interleukin-2 and an analog in which cysteine 125 has been replaced with alanine have been crystallized in a form suitable for x-ray diffraction. The crystals are triclinic, space group P1, with two protein molecules in the unit cell; unit cell parameters are a = 55.8 A, b = 40.1 A, c = 33.7 A, alpha = 90.0 degrees, beta = 109.3 degrees, gamma = 93.2 degrees. The interleukin-2 structure has been solved to 5.5 A resolution using heavy atom isomorphous replacement methods. The resultant low resolution model reveals a significant fraction of alpha helical secondary structure and outlines the overall tertiary structure of the molecule.     

Chemical-genomic profiling: systematic analysis of the cellular targets of bioactive molecules

Chemical-genomic (CG) profiling of bioactive compounds is a powerful approach for drug target identification and mode of action studies. Within the last decade, research focused largely on the development and application of CG approaches in the model yeast Saccharomyces cerevisiae. The success of these methods has sparked interest in transitioning CG profiling to other biological systems to extend clinical and evolutionary relevance. Additionally, CG profiling has proven to enhance drug-synergy screens for developing combinatorial therapies. Herein, we briefly review CG profiling, focusing on emerging cross-species technologies and novel drug-synergy applications, as well as outlining needs within the field.     

Interactions of Fire and Nonnative Species Across an Elevation/Plant Community Gradient in Hawaii Volcanoes National Park

Invasive species interacting with fires pose a relatively unknown, but potentially serious, threat to the tropical forests of Hawaii. Fires may create conditions that facilitate species invasions, but the degree to which this occurs in different tropical plant communities has not been quantified. We documented the survival and establishment of plant species for 2 yr following 2003 wildfires in tropical moist and wet forest life zones in Hawaii Volcanoes National Park, Hawaii. Fires were ignited by lava flows and burned across a steep environmental gradient encompassing two previously burned shrub-dominated communities and three Metrosideros polymorpha forest communities. Fires in all community types were stand replacing, where >95 percent of overstory trees were top killed. Over half (>57%) of the trees survived via basal sprouting, but sprout growth differed among forest communities. Sprout growth (>250,000 cm³) was greatest in the forest community where postfire understory cover was lowest presumably due to thick native Dicranopteris linearis fern litter that remained postfire. In contrast, M. polymorpha sprout growth was much slower (<100,000 cm³) in the two forest communities where there was rapid understory recovery of nonnative ferns Nephrolepis multiflora and invasive grasses Paspalum conjugatum. These results suggest that the rapid establishment of an invasive-dominated understory limited recovery of the overstory dominant M. polymorpha. In contrast to the three forest communities, there were few changes in vegetation composition in the shrubland communities. Nonnative species invasions coupled with repeated fires selectively eliminated fire-sensitive species thereby maintaining these communities in dominance of primarily nonnative, fire-resilient, species.     

Long-Term Effects of Fire on Vegetation Structure and Predicted Fire Behavior in Wyoming Big Sagebrush Ecosystems

Ecosystems - Fire historically occurred across the sagebrush steppe, but little is known about how patterns of post-fire fuel accumulation influence future fire in Wyoming big sagebrush (Artemisia...     

Identification of an S-locus glycoprotein allele introgressed from B. napus ssp. rapifera to B. napus ssp. oleifera.

We have previously described a developmentally regulated mRNA in maize that accumulates in mature embryos and is involved in a variety of stress responses in the plant. The sequence of the encoded 16 kDa protein (MA16) predicts that it is an RNA-binding protein, since it possesses a ribonucleoprotein consensus sequence-type RNA-binding domain (CS-RBD). To assess the predicted RNA binding property of the protein and as a starting point to characterize its function we have used ribohomopolymer-binding assays. Here we show that the MA16-encoded protein binds preferentially to uridine- and guanosine-rich RNAs. In light of these results a likely role for this protein in RNA metabolism during late embryogenesis and in the stress response is discussed.