Phosphorylation of K+ channels in the squid giant axon. A mechanistic analysis

Protein phosphorylation is an important mechanism in the modulation of voltage-dependent ionic channels. In squid giant axons, the potassium delayed rectifier channel is modulated by an ATP-mediated phosphorylation mechanism, producing important changes in amplitude and kinetics of the outward current. The characteristics and biophysical basis for the phosphorylation effects have been extensively studied in this preparation using macroscopic, single-channel and gating current experiments. Phosphorylation produces a shift in the voltage dependence of all voltage-dependent parameters including open probability, slow inactivation, first latency, and gating charge transferred. The locus of the effect seems to be located in a fast 20 pS channel, with characteristics of delayed rectifier, but at least another channel is phosphorylated under our experimental conditions. These results are interpreted quantitatively with a mechanistic model that explains all the data. In this model the shift in voltage dependence is produced by electrostatic interactions between the transferred phosphate and the voltage sensor of the channel.     

<Emphasis Type="Italic">Tuberosciponoceras</Emphasis>: a new dimorphic ammonoid genus from the Upper Albian of Patagonia,Argentina

Tuberosciponoceras insolitum n. gen., n. sp. is a single dimorphic species in the Upper Albian of the Austrat Basin, southern Patagonia. The short-lived genus was characterized by distinct ventral tubercles on all ribs and a deep, trifid internal lobe.     

Vaccination response to tetanus toxoid and 23-valent pneumococcal vaccines following administration of a single dose of abatacept: a randomized,open-label,parallel group study in healthy subjects

The effect of abatacept, a selective T-cell co-stimulation modulator, on vaccination has not been previously investigated. In this open-label, single-dose, randomized, parallel-group, controlled study, the effect of a single 750 mg infusion of abatacept on the antibody response to the intramuscular tetanus toxoid vaccine (primarily a memory response to a T-cell-dependent peptide antigen) and the intramuscular 23-valent pneumococcal vaccine (a less T-cell-dependent response to a polysaccharide antigen) was measured in 80 normal healthy volunteers. Subjects were uniformly randomized to receive one of four treatments: Group A (control group), subjects received vaccines on day 1 only; Group B, subjects received vaccines 2 weeks before abatacept; Group C, subjects received vaccines 2 weeks after abatacept; and Group D, subjects received vaccines 8 weeks after abatacept. Anti-tetanus and anti-pneumococcal (Danish serotypes 2, 6B, 8, 9V, 14, 19F and 23F) antibody titers were measured 14 and 28 days after vaccination. While there were no statistically significant differences between the dosing groups, geometric mean titers following tetanus or pneumococcal vaccination were generally lower in subjects who were vaccinated 2 weeks after receiving abatacept, compared with control subjects. A positive response (defined as a twofold increase in antibody titer from baseline) to tetanus vaccination at 28 days was seen, however, in ≥ 60% of subjects across all treatment groups versus 75% of control subjects. Similarly, over 70% of abatacept-treated subjects versus all control subjects (100%) responded to at least three pneumococcal serotypes, and approximately 25–30% of abatacept-treated subjects versus 45% of control subjects responded to at least six serotypes.     

Antler mineral composition of Iberian red deer <Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis> is related to mineral profile of diet

Previous studies have suggested that antlers are costly bone structures whose mineral composition may change depending on physiological and other factors. This study examined whether nutrition variation associated with deer management influences antler mineral composition and structural characteristics of whole antler. Mineral distribution and bone structure were examined in antlers from two groups of adult Iberian red deer Cervus elaphus hispanicus Hilzheimer, 1909. They were kept under different feeding regimes at an experimental deer farm and a game estate in southeastern Spain. Protein and mineral contents differed between the diet of captive deer and that of deer in the wild. Significant differences were found for Na, Mg, K and protein. Antler composition seems to reflect the diet, as antlers of deer differed in protein, Na, Mg and K, but not in total mineral content, Ca, Fe or Zn. Thus, management conditions related to nutrition are reflected on antler composition.     

Cyanochromes Are Blue/Green Light Photoreversible Photoreceptors Defined by a Stable Double Cysteine Linkage to a Phycoviolobilin-type Chromophore

Phytochromes are a collection of bilin-containing photoreceptors that regulate a diverse array of processes in microorganisms and plants through photoconversion between two stable states, a red light-absorbing Pr form, and a far red light-absorbing Pfr form. Recently, a novel set of phytochrome-like chromoproteins was discovered in cyanobacteria, designated here as cyanochromes, that instead photoconvert between stable blue and green light-absorbing forms Pb and Pg, respectively. Here, we show that the distinctive absorption properties of cyanochromes are facilitated through the binding of phycocyanobilin via two stable cysteine-based thioether linkages within the cGMP phosphodiesterase/adenyl cyclase/FhlA domain. Absorption, resonance Raman and infrared spectroscopy, and molecular modeling of the Te-PixJ GAF (cGMP phosphodiesterase/adenyl cyclase/FhlA) domain assembled with phycocyanobilin are consistent with attachments to the C3¹ carbon of the ethylidene side chain and the C4 or C5 carbons in the A–B methine bridge to generate a double thioether-linked phycoviolobilin-type chromophore. These spectroscopic methods combined with NMR data show that the bilin is fully protonated in the Pb and Pg states and that numerous conformation changes occur during Pb → Pg photoconversion. Also identified were a number of photochromically inactive mutants with strong yellow or red fluorescence that may be useful for fluorescence-based cell biological assays. Phylogenetic analyses detected cyanochromes capable of different signaling outputs in a wide range of cyanobacterial species. One unusual case is the Synechocystis cyanochrome Etr1 that also binds ethylene, suggesting that it works as a hybrid receptor to simultaneously integrate light and hormone signals.Phytochromes (Phys)³ comprise a large and diverse superfamily of photoreceptors that regulate a wide range of physiological responses in plants, fungi, bacteria, and cyanobacteria (1–3). They are unique among photoreceptors by being able to photoconvert between two stable states, a red light-absorbing Pr form that is typically the dark-adapted and biologically inactive conformer and a far-red light-absorbing Pfr form that requires light for its production and is typically the biologically active conformer. By interconverting between Pr and Pfr, Phys act as light-regulated switches in controlling processes ranging from phototaxis and pigmentation in bacteria to seed germination, photomorphogenesis, and flowering time in higher plants.Light absorption by Phys is directed by a bilin (or linear tetrapyrrole) chromophore produced by the oxidative cleavage of heme. Although bacterial and fungal Phys use the immediate cleavage product biliverdin (BV), cyanobacterial and higher plant Phys use phycocyanobilin (PCB) and phytochromobilin, respectively, produced by enzymatic reduction of BV (1, 2). The bilin is then covalently bound autocatalytically to the photosensory unit of the apoprotein, which typically contains a sequence of Per/Arndt/Sim (PAS), cGMP phosphodiesterase/adenyl cyclase/FhlA (GAF), and Phy-associated (PHY) domains. Intimate contact between the bilin and surrounding protein residues then generates the unique photochromic properties of Phys. Recent three-dimensional structures of the Pr form of several bacterial Phys (BphPs) and two cyanobacterial Phys (Cphs) have shown that the bilin is deeply buried within the GAF domain in a ZZZssa configuration and that the connection between the GAF and PAS domains is stabilized by a rare figure-of-eight knot involving the region upstream of the PAS domain being lassoed by a conserved loop within the GAF domain (4–9). Although the structure of Pfr remains unsolved, various physicochemical studies have proposed that photoconversion involves a rotation of one of the three methine bridges between the pyrrole rings (1, 10–14). This rotation then induces much slower thermally driven movements of the protein to initiate signal transduction.In microorganisms, Pfr can activate a variety of signaling systems using output motifs directly appended to the C-terminal end of the photosensory region. The most prevalent are histidine kinase domains that then begin specific two-component phosphorelays (3, 15, 16). Although the output of plant Phys remains unclear, the presence of a C-terminal HK-related domain suggests that they also work as light-regulated protein kinases (17).In addition to the canonical Phys, it has become apparent through phylogenetic and biochemical studies that a heterogeneous collection of Phy-like photoreceptors exists (e.g. Refs. 3 and 18). These include Phys that prefer Pfr as the dark-adapted state (7, 19, 20), Phys that photoconvert from Pr to shorter wavelength-absorbing “near red” or Pnr forms (6, 21), and Phy-like photoreceptors that bind bilins but instead photoconvert between forms with maximal absorption other than red and far-red light (22–25). Often these Phy-like sequences are missing key residues or domains common among canonical Phys, suggesting that they employ novel bilins as chromophores, bind the bilin in different architectures, and/or use distinct photochemistries.One subclass of novel Phy-like photoreceptors present in a number of cyanobacteria, which we have designated cyanochromes (or Cycs) to better distinguish them from Cphs, is exemplified by Synechocystis sp. PCC6803 (Syn) PixJ (or TaxD1, locus sll0041) and its relatives. Syn-PixJ was discovered based on its involvement in blue light-mediated phototaxis in this mesophilic cyanobacterium (26, 27) with its close homolog Te-PixJ (locus tll0569) then found in the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 by sequence similarity (28). Like Cphs, the cyanochromes tested thus far covalently bind PCB but then generate photoreceptors that convert between blue and green light-absorbing forms designated Pb and Pg, respectively (22, 24, 29). Subsequent studies proposed that PCB is converted to phycoviolobilin (PVB) upon attachment to the apoprotein (30). PVB differs from PCB by having a methylene instead of a methine bridge between the A and B pyrrole rings, which blue-shifts the absorption of the chromophore by shortening the π-conjugation system. Phototransformation of Pb to Pg could then occur by a mechanism similar to Phys.How Te-PixJ and related cyanochromes bind PCB to generate more blue-shifted PVB-type chromophores remains unclear. Like Cphs, two cyanochromes examples link PCB via a thioether linkage between a cysteine in the Cyc-GAF domain and the C3¹ carbon of the ethylidene side chain of ring A (24, 28). Additionally, loss of the C4C5 double bond is necessary to generate PVB. One model by Ishizuka et al. (30) from studies with Te-PixJ proposed that the double bond moves from the C4-C5 position to the C2-C3 position by an autoisomerase activity intrinsic to the GAF domain. A more recent model by Rockwell et al. (24) using another Syn-PixJ relative in T. elongatus, Tlr0924, invoked the possibility of a second cysteine that also participates in PCB ligation. This cysteine was proposed to bind the bilin at the C10 position via a reversible thioether linkage. In the dark-adapted Pb state, the second linkage would then be formed to generate a rubin-like chromophore attached to the bridge between the B and C pyrrole rings. This bond would then break upon photoconversion to generate the more π-conjugated green light-absorbing photoproduct Pg.In this report, we employed a number of physicochemical approaches to help resolve the unique chromophore architecture and photochemical properties of cyanochromes, using Te-PixJ as the example. By independently mutagenizing the cysteine that binds the A ring ethylidene (Cys-522 (22)) and that proposed by Rockwell et al. (24) to reversibly bind the bilin at a second site (Cys-494), we demonstrate that both residues form light-stable covalent adducts with a PVB-type chromophore. In addition, we employed various spectroscopic methods to show that the bound PVB is fully protonated as both Pb and Pg, that only one pyrrole ring is active during photoconversion, and that the polypeptide may undergo extensive remodeling as Pb converts to Pg. We identified a set of conserved amino acids in Te-PixJ important for cyanochrome photochemistry, including several that when substituted generate yellow or red fluorescent chromoproteins potentially useful for cell biological applications. Phylogenetic analyses show that cyanochromes are widespread among cyanobacteria with their closest relatives being members of the red/far-red light-absorbing Phy subfamily defined by the absence of the N-terminal PAS domain (31).     

Crop and non-crop productivity in a traditional maize agroecosystem of the highland of Mexico

Background

Haitian migrants played an important role shaping Cuban culture and traditional ethnobotanical knowledge. An ethnobotanical investigation was conducted to collect information on medicinal plant use by Haitian immigrants and their descendants in the Province of Camagüey, Cuba.

Methods

Information was obtained from semi-structured interviews with Haitian immigrants and their descendants, direct observations, and by reviewing reports of traditional Haitian medicine in the literature.

Results

Informants reported using 123 plant species belonging to 112 genera in 63 families. Haitian immigrants and their descendants mainly decoct or infuse aerial parts and ingest them, but medicinal baths are also relevant. Some 22 herbal mixtures are reported, including formulas for a preparation obtained using the fruit of Crescentia cujete. Cultural aspects related to traditional plant posology are addressed, as well as changes and adaptation of Haitian medicinal knowledge with emigration and integration over time.

Conclusion

The rapid disappearance of Haitian migrants' traditional culture due to integration and urbanization suggests that unrecorded ethnomedicinal information may be lost forever. Given this, as well as the poor availability of ethnobotanical data relating to traditional Haitian medicine, there is an urgent need to record this knowledge.     

<i>In vitro</i> Antibacterial Activity of <i>Moringa oleifera</i> Ethanolic Extract against Tomato Phytopathogenic Bacteria

The tomato (Solanum lycopersicum L.) is one of the world’s most important vegetable crops. Still, phytopathogenic bacteria affect the yield and quality of tomato cultivation, like Agrobacterium tumefeciens (At), Clavibacter michiganensis subsp. michiganensis (Cmm), Pseudomonas syringae pv. tomato (Pst), Ralstonia solanacearum (Rs), and Xanthomonas axonopodis (Xa). Synthetic chemical products are used mostly on disease plant control, but overuse generates resistance to bacterial control. This study aimed to evaluate the in vitro antibacterial activity of the ethanolic extract of Moringa oleifera Lam. leaves against At, Cmm, Pst, Rs, and Xa, as well as information about this plant species’ chemical composition. Antibacterial activity against pathogens observed by microplate technique, phytochemical screening, and FTIR analysis revealed different bio-active compounds on ethanolic extracts with antibacterial activity. The growth inhibition rate ranged between 0.08% and 99.94%. The inhibitory concentration, IC50, required to inhibit 50% of At, Cmm, Pst, Rs, and Xa bacterial growth, was 276.67, 350.48, 277.85, 351.49, and 283.22 mg/L, respectively. Inhibition of phytopathogen bacteria’s growth increased as the concentrations of the extract also increased. Moringa oleifera extract can be recommended as a potent bio-bactericide.