Redescription of the Male and Female of <Emphasis Type="Italic">Caliris keralensis</Emphasis> (Vyjayandi et al., 2006) (Mantodea: Caliridinae)

The holotype of Caliris keralensis (Vyjayandi et al. 2006) (Mantodea: Caliridinae) is reviewed along with another paratype female not listed by the authors. The male of this species is re-described in details and is assigned paratype male. Photographs of the specimens are given. Male genital complex is described for better understanding the species.     

Demonstration of an endogenous activator for the Na+, K+-ATPase system

A heat-labile, non-dialysable and protease-sensitive endogenous activator (NaAF) capable of stimulating the Na⁺, K⁺-ATPase system has been demonstrated. The activator (NaAF) activity was partially enriched (about 10 fold) by dialysis (30 kDa cutoff) under negative pressure and pH 4.8 precipitation. The NaAF has been found to occur in the cytosolic fractions of tissues such as the kidney and brain from two different species (rabbit and pig) tested so far. Also, the factor from one tissue stimulates with equal efficacy the Na⁺, K⁺-ATPase systems of other tissues regardless of the species; thus demonstrating universal nature of the activator. Some degree of cross-reactivity was noted between the activating effects of this activator (for the Na⁺,K⁺-ATPase) and that for the H⁺,K⁺-ATPase recently described (J. Biol. Chem. 262:5664–5670, 1987). The purified NaAF obtained from sephacryl S-300 column chromatography activates the pure renal medullary Na⁺,K⁺-ATPase in a dose dependent manner.A preliminary account of this work was published in Fed. Proc. 46(4): 4466, 1987     

Adenyl cyclase of oxyntic cells its association with different cellular membranes

The adenyl cyclase of the oxyntic, or acid-secreting, cells of bullfrog gastric mucosa has been found to be a membrane-bound enzyme. A method has been developed to isolate the adenyl cyclase rich membrane fractions in a hypotonic medium containing dithiothreitol, which has been found to protect the hormonal resposivenes of the adenyl cyclase.Highest specific activity of adenyl cyclase was localized in a light membrane fraction which also had abundant K⁺-stimulated ATPase and K⁺-stimulated $\text{p-}\text{nitrophenyl}$ phophatase and very low cytochrome $\text{c}$ oxidase activty. The three gastric secretagogues tested, namely histamine, pentagastrin and methylcholine, significantly stimulated the adenyl cyclase activity of the light membrane fraction.After treatment with 10 mM Mg⁺ further subfractionation of the light membrane fraction on a sucrose density gradient yielded light membrane subfraction 1, light membrane subfraction 2 and light membrane subfraction 3 in order of increasing densities. The three subfractions had different enzymatic and chemical properties. Adenyl cyclase activity has been found to be distributed in all three subfractions. However, the hormonal responsiveness of the three fractions was quite different. Light membrane subfraction 2 could be stimulated by all three secretagogues, light membrane subfraction 1 by histamine and methylcholine, while light membrane subfraction 3 was refractory to all three secretagogues. On the basis of the cholesterol to phospholipid molar ratio, RNA content, glycoprotein content and the enzymatic data it is suggested that light membrane subfraction 1 and light membrane subfraction 2 are of general plasma-membrane type, while light membrane subfraction 3 is largely of cytoplasmic origin.     

π-π stacking tackled with density functional theory

Through comparison with ab initio reference data, we have evaluated the performance of various density functionals for describing pi-pi interactions as a function of the geometry between two stacked benzenes or benzene analogs, between two stacked DNA bases, and between two stacked Watson-Crick pairs. Our main purpose is to find a robust and computationally efficient density functional to be used specifically and only for describing pi-pi stacking interactions in DNA and other biological molecules in the framework of our recently developed QM/QM approach "QUILD". In line with previous studies, most standard density functionals recover, at best, only part of the favorable stacking interactions. An exception is the new KT1 functional, which correctly yields bound pi-stacked structures. Surprisingly, a similarly good performance is achieved with the computationally very robust and efficient local density approximation (LDA). Furthermore, we show that classical electrostatic interactions determine the shape and depth of the pi-pi stacking potential energy surface.     

Effect of thermal stability on protein adsorption to silica using homologous aldo-keto reductases

Gaining more insight into the mechanisms governing the behavior of proteins at solid/liquid interfaces is particularly relevant in the interaction of high-value biologics with storage and delivery device surfaces, where adsorption-induced conformational changes may dramatically affect biocompatibility. The impact of structural stability on interfacial behavior has been previously investigated by engineering nonwild-type stability mutants. Potential shortcomings of such approaches include only modest changes in thermostability, and the introduction of changes in the topology of the proteins when disulfide bonds are incorporated. Here we employ two members of the aldo-keto reductase superfamily (alcohol dehydrogenase, AdhD and human aldose reductase, hAR) to gain a new perspective on the role of naturally occurring thermostability on adsorbed protein arrangement and its subsequent impact on desorption. Unexpectedly, we find that during initial adsorption events, both proteins have similar affinity to the substrate and undergo nearly identical levels of structural perturbation. Interesting differences between AdhD and hAR occur during desorption and both proteins exhibit some level of activity loss and irreversible conformational change upon desorption. Although such surface-induced denaturation is expected for the less stable hAR, it is remarkable that the extremely thermostable AdhD is similarly affected by adsorption-induced events. These results question the role of thermal stability as a predictor of protein adsorption/desorption behavior.     

Differential effect of imipenem treatment on wild-type and NK cell-deficient CD8 knockout mice during acute intra-abdominal injury

CD8 knockout mice depleted of natural killer (NK) cells by treatment with anti-asialoGM1 (CD8KO/alphaAsGM1 mice) are resistant to injury caused by cecal ligation and puncture (CLP). However, CLP-induced injury is complex. Potential sources of injury include bacterial dissemination, cecal ischemia, and translocation of bacterial toxins. We treated wild-type and CD8KO/alphaAsGM1 mice with imipenem after CLP to decrease bacterial dissemination. Additional mice were subjected to cecal ligation without puncture of the cecal wall or cecal ligation and removal of cecal contents. Imipenem treatment decreased bacterial counts by at least two orders of magnitude. However, all wild-type mice, whether treated with saline or imipenem, died by 42 h after CLP and exhibited significant hypothermia, metabolic acidosis, and high plasma cytokine concentrations. Wild-type mice subjected to cecal ligation without puncture also died, despite very low bacterial counts in blood, but wild-type mice subjected to cecal ligation and washout of cecal contents survived. In CD8KO/alphaAsGM1 mice subjected to CLP, imipenem treatment increased survival from 50% to 100%. After cecal ligation without puncture, long-term survival was 80-90% in CD8KO/alphaAsGM1 mice. Hypothermia, metabolic acidosis, and cytokine production were attenuated in CD8KO/alphaAsGM1 mice compared with wild-type controls. These results indicate that bacterial dissemination is not a major source of injury in wild-type mice after CLP, but the presence of gut flora in the cecal lumen is required for induction of systemic inflammation after cecal injury. CD8KO/alphaAsGM1 mice are resistant to the systemic manifestations of cecal injury.     

Isolation and partial characterization of ribonuclease inhibitor from goat liver

Ribonuclease inhibitor (RI), a 50 kDa protein, has been found both in mammalian and nonmammalian tissues. We have isolated RI from goat liver and partial characterization has been accomplished. For the isolation of RI, DEAE cellulose column chromatography followed by affinity chromatography using CNBr activated Sepharose 4B was performed. The inhibition of ribonucleolytic activity of Ribonuclease A has been checked by an agarose gel based assay. The antiangiogenic property of the protein was tested by the chorioallantoic membrane (CAM) assay. Results indicate inhibition of angiogenesis.     

Retinal-Protein Interactions in Halorhodopsin from Natronomonas pharaonis: Binding and Retinal Thermal Isomerization Catalysis

Halorhodopsin from Natronomonas pharaonis (NpHR) is a member of the retinal protein group and serves as a light-driven chloride pump in which chloride ions are transported through the membrane following light absorption by the retinal chromophore. In this study, we examined two main issues: (1) factors controlling the binding of the retinal chromophore to the NpHR opsin and (2) the ability of the NpHR opsin to catalyze the thermal isomerization of retinal isomers. We have revealed that the reconstitution process of pharaonis HR (NpHR) pigment from its apoprotein and all-trans retinal depends on the pH, and the process has a pK_a of 5.8 ± 0.1. It was proposed that this pK_a is associated with the pK_a of the lysine residue that binds the retinal chromophore (Lys256). The pigment formation is regulated by the concentration of sodium chloride, and the maximum yield was observed at 3.7 M NaCl. The low yield of pigment in a lower concentration of NaCl (< 3 M) may be due to an altered conformation adopted by the apomembrane, which is not capable of forming the pigment. Unexpectedly and unlike the apomembrane of bacteriorhodopsin, NpHR opsin produces pigments with 11-cis retinal and 9-cis retinal owing to the thermal isomerization of these retinal isomers to all-trans retinal. The isomerization rate depends on the pH, and it is faster at a higher pH. The pK_a value of the isomerization process is similar to the pK_a of the binding process of these retinals, which suggests that Lys256 is also involved in the isomerization process. The isomerization is independent of the sodium chloride concentration. However, in the absence of sodium chloride, the apoprotein adopts such a conformation, which does not prevent the isomerization of retinal, but it prevents a covalent bond formation with the lysine residue. The rate and the thermodynamic parameter analysis of the retinal isomerization by NpHR apoprotein led to the conclusion that the apomembrane catalyzes the isomerization via a triplet mechanism.