Membrane-associated pyruvate kinase in developing guinea-pig liver.

During analysis of pyruvate kinase distribution in developing guinea-pig liver it was observed that a substantial proportion of the activity remained associated with the microsomal membrane fraction ('microsomes'). Although some of this could be removed by washing with sucrose, the majority required detergent treatment for liberation, and even then at least one-half remained attached to the microsomes. Estimates of the contribution of this fraction to total cell pyruvate kinase activity indicated that it was more than 50% of the total, and this is likely to be an underestimate because of the continued latency of the enzyme even in the presence of detergent. The susceptibility of the microsomal enzyme, whether released by detergent or sucrose washing, to inactivation by Triton X-100 suggested it to be different from the cytosolic enzyme, which was stable under such conditions. (The microsomal enzyme required the presence of additional protein, such as bovine serum albumin, to maintain stability.) This view was confirmed by DEAE-cellulose chromatography and particularly isoelectric focusing, where the microsomal enzyme was shown to consist of at least four forms, which were distinctly different from those in the cytosol. Those data and the kinetic properties of the four forms in the membrane fraction indicate that the microsomal pyruvate kinase could consist of four counterparts to the cytosolic isoenzyme forms. These results are discussed in relation to the two possible explanations for the phenomenon (not mutually exclusive): that the more hydrophobic membrane forms are precursors of the cytosolic enzyme and that they may be part of functional glycolytic pathway in the microsomes of developing liver.     

The 'aerial plankton' and atmospheric convergence

Airborne migration is one of the most common adaptations for surviving and exploiting habitat variability. One weather feature that airborne migrants sometimes encounter, convergence, has the potential to concentrate populations in localities where climatic conditions have made a habitat temporarily favourable. Studies of migratory insects have now begun to establish which of several forms of atmospheric convergence are most likely to affect population processes.     

Synthesis of a gene for the protein kinase domain of the epidermal growth factor receptor and its expression in Escherichia coli

A gene encoding the protein kinase domain of the epidermal growth factor receptor has been chemically synthesised, cloned and expressed in Escherichia coli. The 942-base-pair gene was constructed by enzymatic ligation of 56 oligonucleotides and cloned into an expression vector downstream of the E. coli trp promoter. Production of active gene product was confirmed by means of a protein kinase assay, demonstrating that the enzymatic activity of the protein kinase domain of the epidermal growth factor receptor is retained after expression in E. coli.     

Analytical model of peptide mass cluster centres with applications

Background  

The elemental composition of peptides results in formation of distinct, equidistantly spaced clusters across the mass range. The property of peptide mass clustering is used to calibrate peptide mass lists, to identify and remove non-peptide peaks and for data reduction.     

Duplication of theDR3Gene on Human Chromosome 1p36 and Its Deletion in Human Neuroblastoma

The humanDR3gene, whose product is also known as Wsl-1/APO-3/TRAMP/LARD, encodes a tumor necrosis factor-related receptor that is expressed primarily on the surface of thymocytes and lymphocytes. DR3 is capable of inducing both NF-κB activation and apoptosis when overexpressed in mammalian cells, although its ligand has not yet been identified. We report here that theDR3gene locus is tandemly duplicated on human chromosome band 1p36.2–p36.3 and that these genes are hemizygously deleted and/or translocated to another chromosome in neuroblastoma (NB) cell lines with amplifiedMYCN.Duplication of at least a portion of theDR3gene, including the extracellular and transmembrane regions but not the cytoplasmic domain, was demonstrated by both fluorescencein situhybridization and genomic Southern blotting. In most NB cell lines, both theDR3and theDR3Lsequences are simultaneously deleted and/or translocated to another chromosome. Finally, DR3/Wsl-1 protein expression is quite variable among these NB cell lines, with very low or undetectable levels in 7 of 17 NB cell lines.