Model building of a protein-protein complexed structure using saturation transfer and residual dipolar coupling without paired intermolecular NOE

For understanding the precise mechanisms of molecular recognition of proteins, three-dimensional structural analyses of the protein-protein complexes are essential. For this purpose, a new method to reveal complex structures was developed with the assistance of saturation transfer (SAT) and residual dipolar coupling (RDC) by heteronuclear NMR experiments, without any paired intermolecular NOE information. The SAT and RDC experiments provide the information of the interfacial residues and the relative orientations of the two protein molecules, respectively. Docking simulation was then made to reconstruct a complex conformation, which satisfies the SAT and RDC data. The method was applied to the CAD-ICAD complex structure, which was previously determined by the NOE-distance geometry method. The quality of the current model was evaluated.     

Effect of Rabbit Anti-Asialo-GM1 (GA1) Polyclonal Antibodies on Neuromuscular Transmission and Acetylcholine-Induced Action Potentials: Neurophysiological and Immunohistochemical Studies

We produced anti-asialo-GM1 (GA1) polyclonal antibodies by sensitizing New Zealand rabbits with GA1 and investigated the epitopes and pathogenic role of anti-GA1 antibodies that appeared in serum. The serum blocked neuromuscular transmission, but not acetylcholine (ACh)-induced potentials, in muscle-spinal cord cocultured cells. The effect was complement independent. The antibodies inhibited voltage-gated Ca2+ channel (VGCC). The epitopes recognized by the antibodies were located in the outer membrane of Schwann cells and motor axons of Wistar rat ventral roots and on motor axons extended from spinal cord to muscle cells in muscle-spinal cocultured cells. The ACh-induced potential was not reduced by the addition of sera, suggesting the blockade is presynaptic. Thus, anti-GA1 antibodies may block neuromuscular transmission by suppressing VGCC on axonal terminals of motor nerves.     

Predominant role of basicity of leaving group in alpha-effect for nucleophilic ester cleavage

It has been found that alpha-effects in nucleophilic reactions, unexpectedly large nucleophilicity due to adjacent unpaired electrons, are strongly dependent on the structure of substrate. The nucleophilic cleavages of 4-nitrobenzoate esters and 4-methylbenzoate esters by HOO- have been systematically investigated in detail. When the leaving groups of substrates are sufficiently good (aryl, 2,2,2-trifluoroethyl, and 2,2-dichloroethyl esters), alpha-effect is evident. However, this effect drastically decreases as the leaving group gets poorer, and is only marginal for the cleavages of 2-fluoroethyl and methyl esters. In the nucleophilic cleavages by salicylaldoxime and acetohydroxamic acid, alpha-effect is also notable only for the esters having good leaving groups. These enormous dependences of alpha-effects on the substrate-structure have been interpreted in terms of the difference in the position of transition-state in the reaction coordinate.     

Evidence that bears are induced ovulators

The objective of this study was to determine if black bears are induced ovulators. We conducted a single experiment with two replicates; each replicate was divided into two arms: females exposed to male bears and females without male exposure. We used laparoscopy to examine ovaries for corpora lutea and measured serum progesterone concentrations. Six of the seven isolated females failed to ovulate, while seven of the eight females exposed to males produced one to four corpora lutea. Furthermore, isolated females had significantly lower progesterone concentrations than females exposed to males. Thus, our data suggest that the American black bear is an induced ovulator. These results may aid biologists in their efforts to reproduce ursids in controlled environments.     

Anti-lipid deposition effect of HMG-CoA reductase inhibitor, pitavastatin, in a rat model of hypertension and hypercholesterolemia

Since the rat is an atherosclerosis-resistant species, the study of atherosclerosis using rats is limited. The present study was undertaken to develop an atherosclerotic model in rats, to investigate the effect of nitric oxide (NO) inactivation and hyperlipidemia, and to evaluate the effect of pitavastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) inhibitor, on NO inactivation and on hyperlipidemia-induced changes in the cardiovascular system. Four-month-old male spontaneously hypertensive hyperlipidemic rats (SHHR) and Sprague-Dawley (SD) rats were used to study 1) the effect of the period of treatment with N(G)-nitro-L-arginine methyl ester (L-NAME, 100 mg/L) on high fat diet (HFD)-treated SHHR and SD rats, and 2) the effect of pitavastatin (Pit, 0.3 mg/kg/day) on the changes in the aorta of L-NAME- and HFD-treated SHHR and SD rats. L-NAME administration for 1 month then HFD feeding for 2 months markedly increased the deposition of lipids and the thickness of the endothelium in SHHR. Continuous L-NAME treatment with HFD produced severe injury and stripped of endothelium in both strains. The plasma total cholesterol of L-NAME + HFD-treated and L-NAME + HFD + Pit-treated SHHR was significantly higher than that of control SHHR. Lipid deposition, however, was comparatively less in the aorta of L-NAME + HFD + Pit-treated SHHR. The concentration of cholesterol in the aorta of control SHHR was significantly lower than that in the aorta of L-NAME + HFD-treated SHHR, whereas that of L-NAME + HFD + Pit-treated SHHR was the same as that in control SHHR. These data indicated that Pit blocked lipid deposition in the aorta of L-NAME + HFD treated SHHR without changing plasma lipid profiles. In conclusion, NO inactivation and HFD induce lipid deposition in the endothelium, and the HMG-CoA reductase inhibitor blocks the deposition in SHHR.     

Identification and characterization of a new pair of immunoglobulin-like receptors LMIR1 and 2 derived from murine bone marrow-derived mast cells

We have identified and characterized two mouse cDNAs in a mouse antigen-stimulated bone marrow-derived mast cell cDNA library, both of which encode type I transmembrane proteins. The genes were closely mapped in the distal region of mouse chromosome 11 and expressed not only in mast cells but also widely in leukocytes. The extracellular domains of their encoded proteins contain a single variable immunoglobulin (Ig) motif sharing about 90% identity with amino acids, showing that they comprise a pair of molecules and belong to the Ig superfamily. We named these molecules leukocyte mono-Ig-like receptor1 and 2 (LMIR1 and 2). The intracellular domain of LMIR1 contains several immunoreceptor tyrosine-based inhibition motifs (ITIMs). When cross-linked, the intracellular domain was tyrosine phosphorylated and capable of recruiting tyrosine phosphatases, SHP-1 and SHP-2 and inositol polyphosphate 5-phosphatase, SHIP. LMIR2, on the other hand, contains a short cytoplasmic tail and a characteristic transmembrane domain carrying two positively charged amino acids associated with three kinds of immunoreceptor tyrosine-based activation motif (ITAM)-bearing molecules, DAP10, DAP12, and FcRgamma. These findings suggest that a new pair of ITIM/ITAM-bearing receptors, LMIR1 and 2, regulate mast cell-mediated inflammatory responses through yet to be defined ligand(s).     

Identification of three novel salicylate 1-hydroxylases involved in the phenanthrene degradation of Sphingobium sp. strain P2

Five sets of large and small subunits of terminal oxygenase (ahdA1[a-e] and ahdA2[a-e]) and a single gene set encoding ferredoxin (ahdA3) and ferredoxin reductase (ahdA4) were found to be scattered through 15.8- and 14-kb DNA fragments of phenanthrene-degrading Sphingobium sp. strain P2. RT-PCR analysis indicated the inducible and specific expression of ahdA3, ahdA4, and three sets of genes for terminal oxygenase (ahdA1[c-e] and ahdA2[c-e]) in this strain grown on phenanthrene. The biotransformation experiments with resting cells of Escherichia coli JM109 harboring recombinant ahd genes revealed that AhdA2cA1c, AhdA1dA2d, and AhdA1eA2e can all function as a salicylate 1-hydroxylase which converts salicylate, a metabolic intermediate of phenanthrene, to catechol in cooperation with the electron transport proteins AhdA3A4. The first two oxygenases exhibited a broad range of substrate specificities such that they also catalyzed the hydroxylation of methyl- and chloro-substituted salicylates to produce their corresponding substituted catechols.     

Oligodeoxynucleotides without CpG motifs work as adjuvant for the induction of Th2 differentiation in a sequence-independent manner

The outcomes of immune responses are regulated by various parameters including how Ags are handled by APCs. In this study, we describe the intrinsic immunomodulatory characteristics of oligodeoxynucleotides (ODNs) that improve the Ag presentation by APCs. ODNs (20-mer) containing CpG motifs induced strong Th1-skewed responses. In contrast, those without CpG motifs enhanced cytokine production by effector Th cells without particular skewing toward Th1 responses or induced the differentiation of unprimed CD4(+) T cells toward Th2 cells. These functional features were prominently envisaged when ODNs were conjugated to the Ag, and were underlain by the facilitated binding of ODN-conjugated Ag to Ia(+) cells. Despite the functional differences between ODNs with CpG motifs and those without CpG motifs, both ODNs bound to Ia(+) cells with similar affinity and kinetics. Immunoenhancing activities of the ODNs were not sequence-dependent; the characteristics, including the facilitation of Ag capture, enhancement of effector Th cell responses, and induction of Th2 cells, were shared by randomly synthesized ODNs conjugated to Ag. This is the first study suggesting that ODNs, independent of the sequences, enhance immune responses through the promoted capture of ODN-conjugated Ag by APCs.