Mechanism of mda-5 Inhibition by Paramyxovirus V Proteins

The RNA helicases encoded by melanoma differentiation-associated gene 5 (mda-5) and retinoic acid-inducible gene I (RIG-I) detect foreign cytoplasmic RNA molecules generated during the course of a virus infection, and their activation leads to induction of type I interferon synthesis. Paramyxoviruses limit the amount of interferon produced by infected cells through the action of their V protein, which binds to and inhibits mda-5. Here we show that activation of both mda-5 and RIG-I by double-stranded RNA (dsRNA) leads to the formation of homo-oligomers through self-association of the helicase domains. We identify a region within the helicase domain of mda-5 that is targeted by all paramyxovirus V proteins and demonstrate that they inhibit activation of mda-5 by blocking dsRNA binding and consequent self-association. In addition to this commonly targeted domain, some paramyxovirus V proteins target additional regions of mda-5. In contrast, V proteins cannot bind to RIG-I and consequently have no effect on the ability of RIG-I to bind dsRNA or to form oligomers.     

Evidence that the nigrotegmental GABAergic projection mediates stereotypy induced by apomorphine and intranigral muscimol

The substantia nigra plays a pivotal role in the relay of output from the striatum. One neural pathway from substantia nigra projects GABAergic fibers to the caudal mesencephalic tegmentum, terminating in the vicinity of the pedunculopontine nucleus (PPN). To evaluate the functional importance of this projection in the mediation of stereotyped behaviors of striatal and nigral origin, we microinjected low doses of the GABA agonist, muscimol, bilaterally into the vicinity of the PPN. This muscimol treatment resulted in a total blockade of all stereotyped behaviors normally elicited by systemic apomorphine or by intranigral muscimol. Blockade was not observed in animals microinjected with muscimol into the dorsal reticular formation, 1 mm above the level of the PPN. Our results indicate that the nigrotegmental projection may play a crucial role in the expression of stereotyped and dyskinetic behaviors of basal ganglia origin.     

Inhibition of enzymes by metal ion-chelating reagents. Theory and new graphical methods of study

1. The mechanism of inhibition of enzymes by metal ion-chelating reagents is discussed and equations derived. 2. Two distinct mechanisms are postulated and graphical methods are given for differentiating between them. 3. Where the metal ion is actually removed from the enzyme to form a co-ordination complex in solution, a procedure is described for obtaining the stability constant for metal-enzyme interaction, the number of metal ions involved and the stoicheiometry of metal ion-ligand interaction.     

Developmental regulation of pectic polysaccharides in the root meristem of Arabidopsis

JIM 5, an antibody that recognizes a relatively unesterifiedpectic epitope, distinguishes between dividing (meristematic)and non-dividing (central cells of the quiescent centre) cellsin the Arabidopsis root tip, indicating that non-dividing cellwalls contain higher levels of relatively unesterified pectinthan dividing cells. JIM 7, an antibody that recognizes a relativelymethyl esterified epitope, labels all cell walls uniformly throughoutthe root, suggesting that there is little variation in the relativelymethyl esterified pectic component in the two cell types. Theseobservations suggest that the characteristics of cell wallsin the root tip result in part from modulations in the amountof unesterified and non-methyl esterified pectin. Key words: Pectin, quiescent centre, roots, Arabidopsis     

A multiplicity of erythrocyte glycolipids of the neolacto series revealed by immuno-thin-layer chromatography with monoclonal anti-I and anti-i antibodies

The thin-layer-chromatography immunostaining procedure was applied to human erythrocyte glycolipids using monoclonal anti-i and anti-I antibodies which are directed against epitopes on linear and branched carbohydrate chains of the neolacto (poly-N-acetyl-lactosamine) series. An examination of native and mild-acid-treated glycolipids from normal adult (I_{adul t} antigen type), neonatal (i_cord) , and I-antigen-deficient adult (i_adult) erythrocytes enabled certain structural inferences to be made as follows: (a) cells of both I and i phenotypes contain a multiplicity of glycolipids of the neolacto series whose backbones consist of 8 or more sugar residues; (b) the octasaccharide backbones are predominantly linear in cells of i phenotype and branched in those of I type; and (c) more complex glycolipids having decasaccharide and larger backbones with both linear and branched sequences occur in erythrocytes of both phenotypes, 0