The regulation of thiomethylgalactoside transport in Clostridium acetobutylicum P262 by inducer exclusion and inducer expulsion mechanisms

Abstract Clostridium acetobutylicum P262 had phosphotransferase systems for glucose and lactose, and the lactose system was inducible. When C. acetobutylicum P262 was provided with glucose and lactose, the cultures grew in a diauxic fashion, and glucose was used preferentially. Cells grown on lactose took up thiomethylgalactoside, and retained this non-metabolizable lactose analog for long periods of time. Because glucose inhibited thiomethylgalactoside uptake and caused the efflux of thiomethylgalactoside that had already been taken up, it appeared that C. acetobutylicum P262 had inducer exclusion and inducer expulsion mechanisms similar to those found in lactic acid bacteria.     

Regulation of the Saccharomyces cerevisiae Srs2 helicase during the mitotic cell cycle, meiosis and after irradiation

The expression of theSRS2 gene, which encodes a DNA helicase involved in DNA repair inSaccharomyces cerevisiae, was studied using anSRS2-lacZ fusion integrated at the chromosomalSRS2 locus. It is shown here that this gene is expressed at a low level and is tightly regulated. It is cell-cycle regulated, with induction probably being coordinated with that of the DNA-synthesis genes, which are transcribed at the G1-S boundary. It is also induced by DNA-damaging agents, but only during the G2 phase of the cell cycle; this distinguishes it from a number of other repair genes, which are inducible throughout the cycle. During meiosis, the expression ofSRS2 rises at a time nearly coincident with commitment to recombination. Sincesrs2 null mutants are radiation sensitive essentially when treated in G1, the mitotic regulation pattern described here leads us to postulate that either secondary regulatory events limit Srs2 activity to G1 cells or Srs2 functions in a repair mechanism associated with replication.     

Touch receptor development and function in Caenorhabditis elegans

Mutations causing a touch-insensitive phenotype in the nematode Caenorhabditis elegans have been the basis of studies on the specification of neuronal cell fate, inherited neurodegeneration, and the molecular nature of mechanosensory transduction. © 1993 John Wiley & Sons, Inc.     

The Perforin Pore Facilitates the Delivery of Cationic Cargos

Cytotoxic lymphocytes eliminate virally infected or neoplastic cells through the action of cytotoxic proteases (granzymes). The pore-forming protein perforin is essential for delivery of granzymes into the cytoplasm of target cells; however the mechanism of this delivery is incompletely understood. Perforin contains a membrane attack complex/perforin (MACPF) domain and oligomerizes to form an aqueous pore in the plasma membrane; therefore the simplest (and best supported) model suggests that granzymes passively diffuse through the perforin pore into the cytoplasm of the target cell. Here we demonstrate that perforin preferentially delivers cationic molecules while anionic and neutral cargoes are delivered inefficiently. Furthermore, another distantly related pore-forming MACPF protein, pleurotolysin (from the oyster mushroom), also favors the delivery of cationic molecules, and efficiently delivers human granzyme B. We propose that this facilitated diffusion is due to conserved features of oligomerized MACPF proteins, which may include an anionic lumen.