Porcine brain natriuretic peptide-like immunoreactivity in rat tissues

The presence of immunoreactive porcine brain natriuretic peptide in rat tissues was studied with a specific radioimmunoassay for porcine brain natriuretic peptide-26. The cross-reactivity of the antiserum used was less than 0.001% with rat atrial natriuretic peptide, rat brain natriuretic peptide-32 and rat brain natriuretic peptide-45. Immunoreactive porcine brain natriuretic peptide was detectable in various tissues of the rat, and high concentrations of immunoreactive porcine brain natriuretic peptide were found in the brain and cardiac atrium, with the highest level in the hypothalamus (159±30 fmol/gram wet tissue, mean±SEM, n=4). Reverse phase high performance liquid chromatography showed that the immunoreactive porcine brain natriuretic peptide of the whole brain and heart extracts eluted mainly at an identical position to synthetic porcine brain natriuretic peptide-26. These findings indicate that porcine brain natriuretic peptide-like substance, distinct from rat brain natriuretic peptide, is present in high concentrations in the rat brain and cardiac atrium.     

Escherichia coli RuvC protein is an endonuclease that resolves the Holliday structure.

Genetic evidence suggests that the Escherichia coli ruvC gene is involved in DNA repair and in the late step of RecE and RecF pathway recombination. To study the biochemical properties of RuvC protein, we overproduced and highly purified the protein. By employing model substrates, we examined the possibility that RuvC protein is an endonuclease that resolves the Holliday structure, an intermediate in genetic recombination in which two double-stranded DNA molecules are linked by single-stranded crossover. RuvC protein cleaves cruciform junctions, which are formed by the extrusion of inverted repeat sequences from a supercoiled plasmid and which are structurally analogous to Holliday junctions, by introducing nicks into strands with the same polarity. The nicked ends are ligated by E.coli or T4 DNA ligases. Analysis of the cleavage sites suggests that DNA topology rather than a particular sequence determines the cleavage site. RuvC protein also cleaves Holliday junctions which are formed between gapped circular and linear duplex DNA by the function of RecA protein. However, it does not cleave a synthetic four-way junction that does not possess homology between arms. The active form of RuvC protein, as studied by gel filtration, is a dimer. This is mechanistically suited for an endonuclease involved in swapping DNA strands at the crossover junctions. From these properties of RuvC protein and the phenotypes of the ruvC mutants, we infer that RuvC protein is an endonuclease that resolves Holliday structures in vivo.     

Properties of the Escherichia coli RuvA and RuvB proteins involved in DNA repair, recombination and mutagenesis

The ruvA and ruvB genes constitute an operon, which is regulated by the SOS system and involved in DNA repair, recombination and mutagenesis. RuvA protein binds to both single-stranded and double-stranded DNA. RuvB protein has weak ATPase activity. RuvA bound to DNA greatly enhances ATPase activity of RuvB. UV-irradiation to supercoiled DNA further enhances the stimulatory effect of RuvA on the RuvB ATPase activity. In the presence of ATP the RuvA-RuvB complex has an activity that renatures cruciform structures formed by heating and gradually cooling supercoiled DNA with an inverted repeat. These findings suggest that the RuvA-RuvB complex interacts with an irregular conformation in damaged DNA and induces conformational changes in DNA using energy provided by ATP hydrolysis, so that it facilitates DNA repair, recombination and error prone replication.     

Purified tyrosine kinases, the EGF receptor kinase and the src kinase, can catalyze the phosphorylation of the band 3 protein from human erythrocytes

The band 3 glycoprotein from human erythrocytes was found to be phosphorylated on tyrosine residues by the purified EGF receptor kinase and the purified src kinase in vitro. Kinetic analysis revealed that Km of the band 3 protein phosphorylation by the EGF receptor kinase was 0.17 microM and 0.65 microM in the absence and presence of EGF (3 X 10(-7)M), respectively, and that in the case of the src kinase it was 0.4 microM. From these data the band 3 protein can be regarded as one of the best substrates common for the EGF receptor kinase and the src kinase in vitro.     

Ferricyanide Induces Flowering by Suppression of Nitrate Assimilation in Lemna paucicostata 6746

Lemna paucicostata 6746, a short-day plant, produced flowerbuds even under continuous light when cultured for 3 days inferricyanide containing ammonium-free medium followed by cultureon nitrogen-rich medium (either nitrate or ammonium). Dailytreatment with ferricyanide in the absence of ammonium for morethan 8 hours, which completely inhibited nitrate reductase activitywithin 6 hours after the addition to the medium, induced daylength-independentflowering even when the ammonium-rich medium was given duringthe remaining hours. The presence of ammonium for 1 hour atthe middle of the 14-h ferricyanide treatment almost completelysuppressed floral induction. (Received March 6, 1986; Accepted June 3, 1986)     

Suppressors of the secY24 mutation: identification and characterization of additional ssy genes in Escherichia coli

We previously reported (Shiba et al., J. Bacteriol. 160:696-701, 1984) the isolation and characterization of the mutation (ssy) that suppresses the protein export defect due to the secY24(Ts) mutation and causes cold-sensitive growth of Escherichia coli. This report describes more systematic isolation of ssy mutations. Among temperature-resistant revertants of the secY24 mutant, 65 mutants were found to be cold sensitive. These cold-sensitive mutations have been classified by genetic mapping. Twenty-two mutations fell into the ssyA class previously described. The remaining mutations were located at five new loci: ssyB at 9.5 min between tsx and lon; ssyD around 3 min; ssyE at 72.5 min near secY; ssyF at 20.5 min within rpsA; and ssyG at 69.0 min near argG. Two predominant classes, ssyA and ssyB, are probably affected in protein synthesis at the elongation step, whereas the ssyF mutant contained an altered form of ribosomal protein S1 (the gene product of rpsA). These cold-sensitive ssy mutations which suppress secY24 may define genes whose function is somehow involved in the secY-dependent protein secretion mechanism. However, the existence of multiple suppressor loci makes it unlikely that all of these genes specify additional components of the export machinery. A delicate balance may exist between the systems for synthesizing and exporting proteins.     

The secY protein can act post-translationally to promote bacterial protein export

Conditionally lethal Escherichia coli mutants in secY (prlA) show defective export of proteins to the periplasm and outer membrane. It has been proposed that this gene and other sec genes must act on pro-OmpA at an early stage of protein synthesis in order to allow later translocation to occur. We have described a temperature-sensitive mutation in which the secYts function is impaired at the nonpermissive temperature (Ito, K. (1984) Mol. Gen. Genet. 197, 204-208). A plasmid bearing the wild-type secY gene under the control of the lactose operon (Shiba, K., Ito, K., Yura, T., and Cerretti, D. P. (1984) EMBO J. 3, 631-635) has been introduced into this mutant strain. We now report that the in vivo chase of pulse-labeled full length pro-OmpA to mature OmpA is accelerated by inducing the synthesis of the wild-type secY protein at the end of the period of pulse labeling. We have also assayed the requirements for secY function for in vitro protein translocation. Membranes derived from secY ts cells which were incubated at 42 degrees C were inactive in vitro in the post-translational uptake and processing of pro-OmpA. Thus, the secY protein can act post-translationally, enhancing the translocation of completed pro-OmpA polypeptide chains across the plasma membrane.     

Refined genetic analysis of the region II che mutants in Salmonella typhimurium

Summary From a detailed complementation analysis of the region II che mutants of Salmonella typhimurium, we have located five che genes, cheA, cheW, cheR, cheB, and cheY. We have shown that corrections are required in the previous assignment of the mutations in four strains: both SL2514 and SL2515 which have been reported to be cheY mutants are cheR mutants, SL2539 is not a cheA but a cheW mutant, and ST171 which has been reported to be a cheZ mutant is a double mutant with defects in both cheA and cheB. Since ST171 is the only cheZ mutant so far isolated, the idea that the cheZ gene might play an essential role in chemotaxis in S. typhimurium as in Escherichia coli has lost its experimental basis. Furthermore, a number of deletion mutants in region II resulting from the excision of Tn10 have been isolated and analysed. From these experiments, we propose that the gene order in region II is flaK-flaE-motA-motB-cheA-cheW-cheR-cheB-cheY-flaM-flaC, which is identical with that in E. coli.     

Inhibitory ca2+-control of movement of beads coated withphysarum myosin along actin-cables inChara internodal cells

Summary The actin-activated ATPase activityPhysarum myosin was shown to be inhibited of M levels of Ca²⁺. To determine if Ca²⁺ regulates ATP-dependent movement ofPhysarum myosin on actin, latex beads coated withPhysarum myosin were introduced intoChara cells by intracellular perfusion. In perfusion solution containing EGTA, the beads moved along the parallel arrays ofChara actin filaments at a rate of 1.0–1.8 m/sec; however, in perfusion solution containing Ca²⁺, the rate reduced to 0.0–0.7 m/sec. The movement of beads coated with scallop myosin, whose actin-activated ATPase activity is activated by Ca²⁺, was observed only in the perfusion solution containing Ca²⁺, indicating that myosin is responsible for the inhibitory effect of Ca²⁺ onPhysarum myosin movement. The involvement of this myosin-linked regulation in the inhibitory effect of Ca²⁺ on the cytoplasmic streaming observed inChara internodal cell andPhysarum plasmodium was discussed.Abbreviations ATP adenosine 5-triphosphate - DTT dithiothreitol - EDTA ethylenediaminetetraacetic acid - EGTA ethyleneglycolbis(-aminoethylether) N,N,N,N-tetraacetic acid - PIPES piperazine-N,N-bis(2-ethanesulfonic acid)     

Continuous production of galacto-oligosaccharides from lactose using immobilized β-galactosidase from Bacillus circulans

Summary -Galactosidase-2 (-d-galactoside galactohydrolase, EC 3.2.1.23) from Bacillus circulans was purified using hydroxyapatite gel chromatography and immobilized onto Duolite ES-762 (phenolformaldehyde resin) and Merckogel (controlled pore silica gel) for continuous production of galacto-oligosaccharides using lactose as the substrate. The maximum amount of ologosaccharides produced by the immobilized enzyme was 35–40% of the total sugar during hydrolysis of 4.56% lactose. Partially purified -galactosidase from B. circulans was also immobilized onto various supports for the same purpose. The stability of the immobilized -galactosidase-2 or partially purified enzyme during a continuous reaction depended on their supports and specific activity. Of the supports tested, Merckogel was best for operational stability. With this support, the enzyme was quite stable with specific activity up to 15 units/g of wet gel; it was reversibly inactivated with more.