Arabidopsis vacuolar sorting mutants (green fluorescent seed) can be identified efficiently by secretion of vacuole-targeted green fluorescent protein in their seeds

Two Arabidopsis thaliana genes have been shown to function in vacuolar sorting of seed storage proteins: a vacuolar sorting receptor, VSR1/ATELP1, and a retromer component, MAIGO1 (MAG1)/VPS29. Here, we show an efficient and simple method for isolating vacuolar sorting mutants of Arabidopsis. The method was based on two findings in this study. First, VSR1 functioned as a sorting receptor for beta-conglycinin by recognizing the vacuolar targeting signal. Second, when green fluorescent protein (GFP) fusion with the signal (GFP-CT24) was expressed in vsr1, mag1/vps29, and wild-type seeds, both vsr1and mag1/vps29 gave strongly fluorescent seeds but the wild type did not, suggesting that a defect in vacuolar sorting provided fluorescent seeds by the secretion of GFP-CT24 out of the cells. We mutagenized transformant seeds expressing GFP-CT24. From approximately 3,000,000 lines of M2 seeds, we obtained >100 fluorescent seeds and designated them green fluorescent seed (gfs) mutants. We report 10 gfs mutants, all of which caused missorting of storage proteins. We mapped gfs1 to VSR1, gfs2 to KAM2/GRV2, gfs10 to the At4g35870 gene encoding a novel membrane protein, and the others to different loci. This method should provide valuable insights into the complex molecular mechanisms underlying vacuolar sorting of storage proteins.     

Production of 2-phenylethanol in roses as the dominant floral scent compound from L-phenylalanine by two key enzymes, a PLP-dependent decarboxylase and a phenylacetaldehyde reductase

We investigated the biosynthetic pathway for 2-phenylethanol, the dominant floral scent compound in roses, using enzyme assays. L-[(2)H8] Phenylalanine was converted to [(2)H8] phenylacetaldehyde and [(2)H8]-2-phenylethanol by two enzymes derived from the flower petals of R. 'Hoh-Jun,' these being identified as pyridoxal-5'-phosphate-dependent L-aromatic amino acid decarboxylase (AADC) and phenylacetaldehyde reductase (PAR). The activity of rose petal AADC to yield phenylacetaldehyde was nine times higher toward L-phenylalanine than toward its D-isomer, and this conversion was not inhibited by iproniazid, a specific inhibitor of monoamine oxidase. Under aerobic conditions, rose petal AADC stoichiometrically produced NH3 together with phenylacetaldehyde during the course of decarboxylation and oxidation, followed by the hydrolysis of L-phenylalanine. Phenylacetaldehyde was subsequently converted to 2-phenylethanol by the action of PAR. PAR showed specificity toward several volatile aldehydes.     

Effects of polyethylene glycol on bovine intestine alkaline phosphatase activity and stability

In this study, we evaluated the effects of polyethylene glycol (PEG) on bovine intestine alkaline phosphatase (BIALP) activity and stability. In the hydrolysis of p-nitrophenylphosphate (pNPP) at pH 9.8 at 20 °C, the k(cat)/K(m) values of BIALP plus 5-15% w/v free PEG with molecular masses of 1, 2, 6, and 20 kDa (PEG1000, PEG2000, PEG6000, and PEG20000 respectively) were 120-140%, 180-300%, 130-170%, and 110-140% respectively of that of BIALP without free PEG (1.8 μM(-1) s(-1)), indicating that activation by PEG2000 was the highest. Unmodified BIALP plus 5% PEG2000 and BIALP pegylated with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine exhibited 1.3-fold higher activity on average than that of BIALP without free PEG under various conditions, including pH 7.0-10.0 and 20-65 °C. The temperatures reducing initial activity by 50% in 30-min incubation of unmodified BIALP plus 5% PEG2000 and pegylated BIALP were 51 and 47 °C respectively, similar to that of BIALP without free PEG (49 °C). These results indicate that the addition of PEG2000 and pegylation increase BIALP activity without affecting its stability, suggesting that they can be used in enzyme immunoassay with BIALP to increase sensitivity and rapidity.     

Molecular and virulence characteristics of an outer membrane-associated RTX exoprotein in <Emphasis Type="Italic">Pasteurella pneumotropica</Emphasis>

Background  

Pasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals. Currently two RTX toxins, PnxIA and PnxIIA, which are similar to hemolysin-like high-molecular-weight exoproteins are known in this species. In this study, we identified and analyzed a further RTX toxin named PnxIIIA and the corresponding type I secretion system.     

Electron tomography reveals diverse conformations of integrin alphaIIbbeta3 in the active state

We used electron tomography to determine the three-dimensional (3D) structure of integrin alphaIIbbeta3 in the active state. We found that we obtained better density maps when we reconstructed a 3D volume for each individual particle in the tilt series rather than to extract the particle-containing subvolumes from a 3D reconstruction of the entire specimen area. The 3D tomographic reconstructions of 100 particles revealed that activated alphaIIbbeta3 adopts many different conformations. An average of all the individual 3D reconstructions nicely accommodated the crystal structure of the alphaVbeta3 headpiece, confirming the locations assigned to the alpha- and beta-subunit in the density map. The most striking finding of our study is the structural flexibility of the lower leg of the beta-subunit as opposed to the conformational stability of the leg of the alpha-subunit. The good fit of the atomic structure of the betaI domain and the hybrid domain in the active state showed that the hybrid domain swings out, and most particles used for tomography are in the active state. Multivariate statistical analysis and classification applied to the set of 3D reconstructions revealed that more than 90% reconstructions are grouped into the classes that show the active state. Our results demonstrate that electron tomography can be used to classify complexes with a flexible structure such as integrins.     

A polysaccharide deacetylase homologue, PdaA, in Bacillus subtilis acts as an N-acetylmuramic acid deacetylase in vitro

A polysaccharide deacetylase homologue, PdaA, was determined to act as an N-acetylmuramic acid deacetylase in vitro. Histidine-tagged truncated PdaA (with the putative signal sequence removed) was overexpressed in Escherichia coli cells and purified. Measurement of deacetylase activity showed that PdaA could deacetylate peptidoglycan treated with N-acetylmuramoyl-L-alanine amidase CwlH but could not deacetylate peptidoglycan treated with or without DL-endopeptidase LytF (CwlE). Reverse-phase high-performance liquid chromatography and mass spectrometry (MS) and MS-MS analyses indicated that PdaA could deacetylate the N-acetylmuramic acid residues of purified glycan strands derived from Bacillus subtilis peptidoglycan.     

Adiponectin inhibits the binding of low-density lipoprotein to biglycan, a vascular proteoglycan

The aim of this study was to test the possibility that adiponectin has an antiatherogenic effect through the inhibition of LDL binding to proteoglycans, an initial event in atherogenesis. Both full-length and globular adiponectin inhibited LDL binding in a dose-dependent manner. Both types of adiponectin bound to biglycan in a dose-dependent manner. Immunoprecipitation and immunoblotting analysis showed interaction of full-length adiponectin with LDL. Pretreatment of biglycan with globular adiponectin prior to LDL addition diminished the inhibitory effect, while pretreatment with full-length adiponectin retained the effect. This is a new antiatherogenic property that appears independent of the receptor-mediated hormonal action of adiponectin.