Pseudorabies virus glycoproteins gII and gp50 are essential for virus penetration.

Pseudorabies virus (PrV) glycoproteins gII and gp50 are major constituents of the viral envelope and targets of neutralizing monoclonal antibodies. Both are homologs of essential glycoproteins found in herpes simplex virus, gB (gII) and gD (gp50). We recently isolated a gII-negative PrV deletion mutant on complementing cell lines and established the essential character of gII for PrV replication (I. Rauh, F. Weiland, F. Fehler, G. Keil, and T.C. Mettenleiter, J. Virol. 65: 621-631, 1991). In this report, we describe the isolation of a gp50-negative PrV mutant after constructing cell lines that constitutively express gp50 and phenotypically complement the gp50 defect. Analysis of the gp50- mutant proved that gp50 is essential for PrV replication. Further studies showed that both gII and gp50 are required for viral penetration into target cells. The penetration defect in the gII and gp50 deletion mutants could be overcome by experimental polyethylene glycol-induced membrane fusion. Surprisingly, whereas gII proved to be essential for both penetration and cell-cell spread of the virus, gp50 was required only for penetration and appeared dispensable for direct cell-cell spread.     

Pharmacology of insect GABA receptors

A GABA-operated Cl^– channel that is bicuculline-insensitive is abundant in the nervous tissue of cockroach, in housefly head preparations and thorax/abdomen preparations, and in similar preparations from several insect species. Bicuculline-insensitive GABA-operated Cl^– channels, which are rare in vertebrates, possess sites of action of benzodiazepines, steroids and insecticides that are pharmacologically-distinct from corresponding sites on vertebrate GABA_A receptors. The pharmacological profile of the benzodiazepine-binding site linked to an insect CNS GABA-operated Cl^– channel resembles more closely that of vertebrate peripheral benzodiazepine-binding sites. Six pregnane steroids and certain polychlorocycloalkane insecticides, which are active att-butylbicy-clophosphorothionate (TBPS)-binding sites, also differ in their effectiveness on vertebrate and insect GABA receptors. Radioligand binding and physiological studies indicate that in insects there may be subtypes of the GABA receptor. Molecular biology offers experimental approaches to understanding the basis of this diversity.Special issue dedicated to Dr. Eugene Roberts     

A simple recipe for setting up the flux equations of cyclic and linear reaction schemes of ion transport with a high number of states: The arrow scheme

The calculation of flux equations or current-voltage relationships in reaction kinetic models with a high number of states can be very cumbersome. Here, a recipe based on an arrow scheme is presented, which yields a straightforward access to the minimum form of the flux equations and the occupation probability of the involved states in cyclic and linear reaction schemes. This is extremely simple for cyclic schemes without branches. If branches are involved, the effort of setting up the equations is a little bit higher. However, also here a straightforward recipe making use of so-called reserve factors is provided for implementing the branches into the cyclic scheme, thus enabling also a simple treatment of such cases.