The effect of auxin on ribosomal protein phosphorylation of germinating maize (Zea mays) tissues was investigated. Twodimensional gel electrophoresis and autoradiography of [32P] ribosomal protein pattems for natural and synthetic auxin-treated tissues were performed. Both the rate of 32P incorporation and the electrophoretic pattems were dependent on 32P pulse length, suggesting that active protein phosphorylation-dephosphorylation occurred in small and large subunit proteins, in control as well as in auxin-treated tissues. The effect of ribosomal protein phosphorylation on in vitro translation was tested. Measurements of poly(U) translation rates as a function of ribosome concentration provided apparent Km values significantly different for auxintreated and nontreated tissues. These findings suggest that auxin might exert some kind of translational control by regulating the phosphorylated status of ribosomal proteins.

A simple scheme for the purification of pyruvate carboxylase from rat liver mitochondria is described. It is rapid and provides high-purity pyruvate carboxylase with excellent yield and reproducibility. The final enzyme preparations appear to be homogeneous by the following criteria: elution behaviour on molecular-sizing matrix, SDS/polyacrylamide-gel electrophoresis, Ouchterlony double-diffusion analysis and Western blotting. Detection and quantification of nanogram amounts of pyruvate carboxylase (apo and holo forms) in total tissue homogenates by immuno-blotting and by enzyme-linked immunosorbent assay are described. The data provided suggest that under normal physiological conditions (both in vivo and in vitro) essentially all the pyruvate carboxylase molecules are biotinylated.

Actinobacillus suis secretes metalloproteases into its medium. These secreted proteins, when concentrated by precipitation with 70% (NH4)2SO4 or methanol, displayed proteolytic activity at >200 kDa molecular mass bands in 10% polyacrylamide gels copolymerized with bovine casein (1%). They showed activity in a broad pH range (from pH 5 to pH 10) and were inhibited by 20 mM EDTA or EGTA, but could be reactivated by calcium. They were found heat stable at 40 degrees C, 50 degrees C, 60 degrees C, and 70 degrees C, but their activity diminished at 80 degrees C or higher. They degraded pig and bovine IgG and cross-reacted with a polyclonal serum against a high molecular mass secreted protease from A. pleuropneumoniae. Extracellular proteases could play a role in diseases caused by A. suis.