Alteration of hemolymph polypeptides in Manduca sexta larvae parasitized by Cotesia congregata: A two-dimensional electrophoretic analysis and comparison with major bacteria-induced proteins

Analyses using one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) previously demonstrated that parasitization by the braconid wasp Cotesia congregata significantly alters the normal hemolymph polypeptide profile of host Manduca sexta larvae. In the present study two-dimensional gel analyses corroborated our earlier findings and provided additional evidence that multiple parasitism-specific polypeptides were induced, which varied according to the stage of development of the wasps. Parasitization additionally elicited changes in the total protein concentration detected in the blood. Initially an elevation was observed, with newly parasitized larvae exhibiting a twofold elevation in hemolymph protein concentration by 12–24 h postoviposition. In contrast, terminal-stage hosts with second instar parasites had significantly less protein in the hemolymph, likely due to reduced growth and inhibition of arylphorin synthesis by the fat body during the final stages of parasitism. Comparison of the array of hemolymph polypeptides produced in unparasitized larvae injected with 10⁶cells of the gram-negative bacterium Enterobacter cloacae with those proteins induced by parasitization indicated the two classes are different. Our findings confirm that the hostresponse to parasitism is a specific one, and not mimicked by bacterial challenge. Duringshort-term in vitro culture of wasp larvae dissected from the host hemocoel, several proteins were detected in the medium using SDS - PAGE, with their appearance in vitro suggestive of secretion by the wasps in vivo. Moreover, hemolymph from the parasites had significant amounts of putative host proteins, including an arylphorin - like polypeptide and a protein with a mobility similar to that of insecticyanin. Thus, a dynamic interchange of proteins may occur, with the parasites accumulating host proteins while simultaneously secreting a variety of factors into the host hemocoel.     

mRNA Targeting to Endoplasmic Reticulum Precedes Ago Protein Interaction and MicroRNA (miRNA)-mediated Translation Repression in Mammalian Cells

MicroRNA (miRNA) binds to the 3′-UTR of its target mRNAs to repress protein synthesis. Extensive research was done to understand the mechanism of miRNA-mediated repression in animal cells. Considering the progress in understanding the mechanism, information about the subcellular sites of miRNA-mediated repression is surprisingly limited. In this study, using an inducible expression system for an miRNA target message, we have delineated how a target mRNA passes through polysome association and Ago2 interaction steps on rough endoplasmic reticulum (ER) before the miRNA-mediated repression sets in. From this study, de novo formed target mRNA localization to the ER-bound polysomes manifested as the earliest event, which is followed by Ago2 micro-ribonucleoprotein binding, and translation repression of target message. Compartmentalization of this process to rough ER membrane ensures enrichment of miRNA-targeted messages and micro-ribonucleoprotein components on ER upon reaching a steady state.     

Molecular evidence to reconcile taxonomic instability in mahseer species (Pisces: Cyprinidae) of India

The mahseers are an important group of fishes endemic to Asia with most species considered threatened. Conservation plans to save declining wild populations are hindered by unstable taxonomy, and detailed systematic review could form a solid platform for future management and conservation. D-loop and cytochrome c oxidase I (COI) mtDNA sequences were examined in nine mahseer species of Tor, Neolissochilus, and Naziritor. Pseudogenes amplified in a portion of the species limited the utility of the D-loop region. ABGD analysis, NJ, ML, and MP methods and genetic distance (TrN?+?I?+?G) using COI data revealed concordant species delimiting patterns. The three genera were monophyletic, separated as distinct clades (TrN?+?I?+?G 0.064 to 0.106), and Naziritor was flagged as a separate genus, distinct from Puntius (TrN?+?I?+?G 0.196). Out of seven nominal species known for Tor cogeners from India, only five were recovered with mtDNA data (TrN?+?I?+?G 0.000 to 0.037) and two species could not be distinguished with the molecular data set employed. Tor mosal, synonymized as Tor putitora, was rediscovered as a distinct species (TrN?+?I?+?G 0.031) based on its type locality. Tor mussulah was confirmed as a separate species (TrN?+?I?+?G 0.019 to 0.026). Two valid species, Tor macrolepis and T. mosal mahanadicus, were not distinct from T. putitora (TrN?+?I?+?G 0.00). The high divergence with mtDNA data failed to validate T. mosal mahanadicus as a subspecies of T. mosal (TrN?+?I?+?G 0.031). Morphological outliers discovered within the distribution range of Tor tor (TrN?+?I?+?G 0.022 to 0.025) shared the same lineage with T. putitora (TrN?+?I?+?G 0.002 to 0.005), indicating a new extended distribution of the Himalayan mahseer T. putitora in the rivers of the Indian central plateau. The findings indicate the need for integrating molecular and morphological tools for taxonomic revision of the Tor and Naziritor genera, so that taxa are precisely defined for accurate in situ and ex situ conservation decisions.     

The neonatal Fc receptor (FcRn) binds independently to both sites of the IgG homodimer with identical affinity

The neonatal Fc receptor (FcRn) is expressed by cells of epithelial, endothelial and myeloid lineages and performs multiple roles in adaptive immunity. Characterizing the FcRn/IgG interaction is fundamental to designing therapeutic antibodies because IgGs with moderately increased binding affinities for FcRn exhibit superior serum half-lives and efficacy. It has been hypothesized that 2 FcRn molecules bind an IgG homodimer with disparate affinities, yet their affinity constants are inconsistent across the literature. Using surface plasmon resonance biosensor assays that eliminated confounding experimental artifacts, we present data supporting an alternate hypothesis: 2 FcRn molecules saturate an IgG homodimer with identical affinities at independent sites, consistent with the symmetrical arrangement of the FcRn/Fc complex observed in the crystal structure published by Burmeister et al. in 1994. We find that human FcRn binds human IgG1 with an equilibrium dissociation constant (K_D) of 760 ± 60 nM (N = 14) at 25°C and pH 5.8, and shows less than 25% variation across the other human subtypes. Human IgG1 binds cynomolgus monkey FcRn with a 2-fold higher affinity than human FcRn, and binds both mouse and rat FcRn with a 10-fold higher affinity than human FcRn. FcRn/IgG interactions from multiple species show less than a 2-fold weaker affinity at 37°C than at 25°C and appear independent of an IgG''s variable region. Our in vivo data in mouse and rat models demonstrate that both affinity and avidity influence an IgG''s serum half-life, which should be considered when choosing animals, especially transgenic systems, as surrogates.     

Interaction of human 3-phosphoglycerate kinase with L-ADP, the mirror image of D-ADP

l-Nucleoside-analogues, mirror images of the natural d-nucleosides, are a new class of antiviral and anticancer agents. In the cell they have to be phosphorylated to pharmacologically active triphosphate forms, the last step seems to involve human 3-phosphoglycerate kinase (hPGK). Here we present a steady state kinetic and biophysical study of the interaction of the model compound l-MgADP with hPGK. l-MgADP is a good substrate with k_cat and K_m values of 685 s⁻¹ and 0.27 mM, respectively. Double inhibition studies suggest that l-MgADP binds to the specific adenosine-binding site and protects the conformation of hPGK molecule against heat denaturation, as detected by microcalorimetry. Structural details of the interaction in the enzyme active site are different for the d- and l-enantiomers (e.g. the effect of Mg²⁺), but these differences do not prevent the occurrence of the catalytic cycle, which is accompanied by the hinge-bending domain closure, as indicated by SAXS measurements.     

High Capacity and High‐Rate NASICON‐Na3.75V1.25Mn0.75(PO4)3 Cathode for Na‐Ion Batteries via Modulating Electronic and Crystal Structures

Sodium superionic conductor (NASICON) cathodes are attractive for Na‐ion battery applications as they exhibit both high structural stability and high sodium ion mobility. Herein, a comprehensive study is presented on the structural and electrochemical properties of the NASICON‐Na_3+yV_2?yMn_y(PO₄)₃ (0 ≤ y ≤ 1) series. A phase miscibility gap is observed at y = 0.5, defining two solid solution domains with low and high Mn contents. Although, members of each of these domains Na_3.25V_1.75Mn_0.25(PO₄)₃ and Na_3.75V_1.25Mn_0.75(PO₄)₃ reversibly exchange sodium ions with high structural integrity, the activity of the Mn³⁺/Mn²⁺ redox couple is found to be absent and present in the former and latter candidate, respectively. Galvanostatic cycling and rate studies reveal higher capacity and rate capability for the Na_3.75V_1.25Mn_0.75(PO₄)₃ cathode (100 and 89 mA h g^?1 at 1C and 5C rate, respectively) in the Na_3+yV_2?yMn_y(PO₄)₃ series. Such a remarkable performance is attributed to optimum bottleneck size (≈5 Ų) and modulated V‐ and Mn‐redox centers as deduced from Rietveld analysis and DFT calculations, respectively. This study shows how important it is to manipulate electronic and crystal structures to achieve high‐performance NASICON cathodes.     

Histone acetyltransferase-1 regulates integrity of cytosolic histone H3-H4 containing complex

Amounts of soluble histones in cells are tightly regulated to ensure supplying them for the newly synthesized DNA and preventing the toxic effect of excess histones. Prior to incorporation into chromatin, newly synthesized histones H3 and H4 are highly acetylated in pre-deposition complex, wherein H4 is di-acetylated at Lys-5 and Lys-12 residues by histone acetyltransferase-1 (Hat1), but their role in histone metabolism is still unclear. Here, using chicken DT 40 cytosolic extracts, we found that histones H3/H4 and their chaperone Asf1, including RbAp48, a regulatory subunit of Hat1 enzyme, were associated with Hat1. Interestingly, in HAT1-deficient cells, cytosolic histones H3/H4 fractions on sucrose gradient centrifugation, having a sedimentation coefficient of 5–6S in DT40 cells, were shifted to lower molecular mass fractions, with Asf1. Further, sucrose gradient fractionation of semi-purified tagged Asf1-complexes showed the presence of Hat1, RbAp48 and histones H3/H4 at 5–6S fractions in the complexes. These findings suggest the possible involvement of Hat1 in regulating cytosolic H3/H4 pool mediated by Asf1-containing cytosolic H3/H4 pre-deposition complex.     

Cryoenzymic studies on myosin subfragment 1: perturbation of an enzyme reaction by temperature and solvent

The effects of temperature and solvent on myosin subfragment 1 ATPase have been studied. Under all of the conditions used the data could be fitted to the Bagshaw - Trentham pathway: (formula; see text) Ethylene glycol (40%) was used as the cryosolvent ; this makes K1 and k+2 measurable and allows for temperature studies over an extensive temperature range (+35 to -20 degrees C) and thus to reasonably accurate thermodynamic parameters. The following techniques were used: ATP chase (for K1 and k+2); Pi burst (k+2 or k+3 + k-3); single-turnover Pi burst [k0 = k +4K3 /(1 + K3)] absorption stopped flow (k+2 or k+3 + k-3); steady state (k+6 or k0). Myosin provides examples of causes for nonlinear Arrhenius and van't Hoff plots. A temperature-induced structural change is exemplified by a "jump" in an Arrhenius plot of k+2 and "breaks" in van't Hoff plots of K1 and K3. A change in rate-limiting step is illustrated from stopped-flow experiments ( kobsd approximately k+2 at low and approximately k+3 + k-3 at high temperatures) and steady-state experiments (kcat approximately k+6 at low and approximately k0 at high temperatures). A third cause is illustrated by k0: an Arrhenius plot of k0 is nonlinear since there is a break in K3. These studies illustrate the use of temperature perturbation as a way of revealing reaction intermediates and of defining the conditions required for the isolation of a particular intermediate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetics of the allosteric transition of aspartate transcarbamylase. Chemical quench studies

Using a chemical quench device, the rate of synthesis of carbamyl aspartate from the substrates aspartate and carbamyl phosphate was followed as a function of the time between mixing the enzyme with substrates and quenching with trichloroacetic acid. This function, which is linear at long times, shows (at 4 degrees C) a transient lag phase of product of roughly 10 ms. However, when the catalytic subunit (in which the enzymatic activity is desensitized) is used instead of the enzyme, the lag disappears. Therefore the lag seems to be associated with the control functions of the enzyme, i.e. to represent the allosteric transition involved in substrate-substrate (homotropic) co-operativity. Thus the relaxation time for the activation process is roughly 10 ms. The implications of these results are examined.     

Use of interposed polytetrafluorethylene (PTFE) graft in distal splenorenal shunt

Two patients with massive upper gastrointestinal hemorrhages required transsplenic decompression of the esophageal varices, but because technical difficulties precluded tension-free anastomoses, interposition of PTFE grafts was used to solve these difficult situations.