The receptor of bacteriophage lambda: evidence for a biosynthesis dependent on lipid synthesis

Inhibition of lipid synthesis in cerulenin-treated cells or in a mutant strain defective in sn-glycerol-3-phosphate acyltransferase after glycerol deprivation, results in a marked decrease of insertion of lamB protein into the outer membrane. No lambda receptor was found in any other cell compartment or in the medium under these conditions. The LamB protein synthesis was inhibited by about 70% in the absence of lipid synthesis. The residual 30% protein produced during inhibition of fatty-acid or phospholipid synthesis, was probably incorporated into the outer membrane since no further incorporation was observed after resumption of these syntheses. Besides OmpF and OmpC protein [Bocquet-Pagès, C., Lazdunski, C., and Lazdunski, A. (1981) Eur. J. Biochem. 118, 105-111], at least four other proteins of the outer membrane are also subject to alteration of levels in the absence of lipid synthesis. Under these conditions the uptake of maltose, like the uptake of 5'AMP [Bocquet-Pagès, C., Lazdunski, C., and Lazdunski, A. (1981) Eur. J. Biochem. 118, 105-111], was inhibited as much as 60%. These results are discussed with regard to the biosynthesis and assembly of the outer membrane proteins.     

Specificity of antierythrocyte autoantibodies secreted by a NZB-derived hybridoma and NZB peritoneal cells

The specificity of monoclonal IgM antierythrocyte autoantibody produced by a NZB-derived hybridoma and the specificity of autoantibodies produced by uninduced NZB peritoneal cells in culture were determined. Supernatant fluids from cultures of hybridoma and peritoneal cells reacted in direct hemagglutination assays with bromelin-treated mouse erythrocytes, and, to a lesser extent, with sheep red blood cells; no agglutination was observed with intact mouse red blood cells or human O⁺ erythrocytes. These results suggest the presence of previously characterized anti-HB, but not anti-X or cold reactive autoantibodies, with a cross-reaction between antigenic constituents on sheep and bromelin-treated mouse erythrocytes. Specificity was affirmed by neutralization of agglutination or of direct hemolysis of bromelin-treated mouse erythrocytes with partially purified SEA-HB, the soluble plasma analog of the erythrocyte-bound HB autoantigen. Plaque formation in direct plaque-forming cell assays by both hybridoma and peritoneal cells was specifically inhibited by SEA-HB. These results demonstrate that NZB-derived hybridoma as well as NZB peritoneal cells secrete anti-HB autoantibody, an autoantibody that spontaneously appears in the serum of NZB as well as other strains of mice.     

Conformational studies on muscular parvalbumins cooperative binding of calcium (II) to parvalbumins.

1H NMR and ORD were used to characterize the respective variations of tertiary structure and secondary structure of parvalbumins with calcium content ((Pa(O), without calcium and PaCa2 calcium saturated) and temperature. It has been observed that the tertiary structure can be lost without significant variation of the helical content. Cooperative binding of calcium to Pa(O) has been shown by NMR spectroscopy under low ionic strength conditions and at neutral pH. The present study shows that the calcium binding affinity of parvalbumin is dependent on the tertiary structure. Calcium binding and calcium release functions of parvalbumins in the muscle may be controlled by their tertiary structure.     

Ecological zonation of the hyperhaline estuary of the Casamance River (Senegal): Foraminifera,zooplankton and abiotic variables

Due to a long-lasting drought afflicting the Sahel, the Casamance River has been transformed into a hyperhaline estuary, with salinities up to 170% at a distance of 210 km from the sea. Foraminifera and zooplankton populations both show a marked decrease in the number of species in increasingly confined water, the distribution of species being closely related to the evolution of abiotic variables. Our three-prong study allowed us to identify six zones, upwards from the sea. The uppermost ones are characterized by drastic conditions which considerably reduce the number of species. Therefore, the populations of Foraminifera, zooplankton and even fish become oligo or mono specific. The Casamance River appears to fit quite well into the general rules concerning hyperhaline environments. However, it shows some peculiar features which are: the large dimensions of the hyperhaline estuary (over 230 km long and over 5 km wide in the lower course); peak salinities among the highest known for a permanently open estuary (up to 170%); and water remaining trapped inside the river for several years.