A Carbapenem-Resistant Pseudomonas aeruginosa Isolate Harboring Two Copies of blaIMP-34 Encoding a Metallo-β-Lactamase

A carbapenem-resistant strain of Pseudomonas aeruginosa, NCGM1984, was isolated in 2012 from a hospitalized patient in Japan. Immunochromatographic assay showed that the isolate was positive for IMP-type metallo-β-lactamase. Complete genome sequencing revealed that NCGM1984 harbored two copies of bla_IMP-34, located at different sites on the chromosome. Each bla_IMP-34 was present in the same structures of the class 1 integrons, tnpA(ISPa7)-intI1-qacG-bla_IMP-34-aac(6'')-Ib-qacEdelta1-sul1-orf5-tniBdelta-tniA. The isolate belonged to multilocus sequence typing ST235, one of the international high-risk clones. IMP-34, with an amino acid substitution (Glu126Gly) compared with IMP-1, hydrolyzed all β-lactamases tested except aztreonam, and its catalytic activities were similar to IMP-1. This is the first report of a clinical isolate of an IMP-34-producing P. aeruginosa harboring two copies of bla_IMP-34 on its chromosome.     

Mucopolysaccharidosis type VII: Characterization of mutations and molecular heterogeneity

We identified two different exonic point mutations causing beta-glucuronidase (beta G1) deficiency in two Japanese patients with mucopolysaccharidosis type VII (MPSVII). Enzyme assay of lysates of the lymphocytes and cultured fibroblasts showed little residual activity. The beta G1-specific mRNA levels were normal, as determined by northern blot analysis. Mutated cDNA clones, including the entire coding sequence, were isolated using the polymerase chain reaction (PCR) products derived from beta G1-deficient fibroblasts. Sequence analysis of the full-length mutated cDNAs showed C----T transitions, which resulted in a single Ala619----Val change (case 1, a 24-year-old male) and a Arg382----Cys change (case 2, a 7-year-old female). The former change was revealed by a loss of the cleavage site for the Fnu4HI in the mutated cDNA. On the basis of the loss of Fnu4HI restriction site, the patient (case 1) was a homozygote with this mutation. The mutational change in patient 2 was confirmed by direct sequencing and by demonstrating heterozygosity for the mutation in her parents. The Ala619----Val and Arg382----Cys mutations each disrupt a different domain which is highly conserved among human, rat, and Escherichia coli beta G1s. Each of these two amino acid changes reduced the beta G1 activity of the corresponding mutant beta G1 expressed following transfection of COS cells with expression vectors harboring the mutated cDNAs.     

Computational models explain the oligosaccharide specificity of cyanovirin-N

The prokaryotic lectin cyanovirin-N (CV-N) is a potent inhibitor of HIV envelope-mediated cell entry, and thus is a leading candidate among a new class of potential anti-HIV microbicides. The activity of CV-N is a result of interactions with the D1 arm of high-mannose oligosaccharides on the viral glycoprotein gp120. Here, we present computationally refined models of CV-N recognition of the di- and trisaccharides that represent the terminal three sugars of the D1 arm by each CV-N binding site. These models complement existing structural data, both from NMR spectroscopy and X-ray crystallography. When used with a molecular dynamics/continuum electrostatic (MD/PBSA) approach to compute binding free energies, these models explain the relative affinity of each site for the two saccharides. This work presents the first validation of the application of continuum electrostatic models to carbohydrate-protein association. Taken as a whole, the results both provide models of CV-N sugar recognition and demonstrate the utility of these computational methods for the study of carbohydrate-binding proteins.     

Efficient large-scale protein production of larvae and pupae of silkworm by Bombyx mori nuclear polyhedrosis virus bacmid system

Silkworm is one of the most attractive hosts for large-scale production of eukaryotic proteins as well as recombinant baculoviruses for gene transfer to mammalian cells. The bacmid system of Autographa californica nuclear polyhedrosis virus (AcNPV) has already been established and widely used. However, the AcNPV does not have a potential to infect silkworm. We developed the first practical Bombyx mori nuclear polyhedrosis virus bacmid system directly applicable for the protein expression of silkworm. By using this system, the green fluorescence protein was successfully expressed in silkworm larvae and pupae not only by infection of its recombinant virus but also by direct injection of its bacmid DNA. This method provides the rapid protein production in silkworm as long as 10 days, is free from biohazard, thus will be a powerful tool for the future production factory of recombinant eukaryotic proteins and baculoviruses.     

Ferredoxin-dependent glutamate synthase moonlights in plant sulfolipid biosynthesis by forming a complex with SQD1

UDP-sulfoquinovose synthase, SQD1, catalyzes the transfer of sulfite to UDP-glucose giving rise to UDP-sulfoquinovose, which is the head group donor for the biosynthesis of the plant sulfolipid sulfoquinovosyldiacylglyerol. The native SQD1 enzyme of spinach exists as a 250 kDa heteroprotein complex with much higher affinity for the substrate sulfite than the recombinant SQD1 protein itself. The SQD1 protein co-purified with nine proteins. Likely binding partners included rubisco activase, HSP70, and ferredoxin-dependent glutamate synthase (FdGOGAT). While the first two proteins are known to interact with many other proteins, the identification of FdGOGAT was most intriguing because this 160kDa protein contains an FMN cofactor known to bind sulfite in vitro. Using different constructs expressing recombinant forms of the multidomain protein FdGOGAT, it was demonstrated that the FMN-binding domain of FdGOGAT is essential for specific binding of the protein to SQD1. A model suggests that FdGOGAT could channel sulfite to SQD1.     

Analysis of ascidian <Emphasis Type="Italic">Not</Emphasis> genes highlights their evolutionarily conserved and derived features of structure and expression in development

The ascidian larva is often regarded as an organism close to the ancestral form of chordates, while it is generally accepted that the Spemanns organizer is absent from ascidian embryos. Not is one of the genes expressed in the organizer to execute functions in vertebrate embryos. To address the extent of conservation of Not gene expression among ascidians and vertebrates, we examined the structure and developmental expression of Not of the two distantly related ascidian species, Halocynthia and Ciona. Putative ascidian Not proteins were noted by the absence of one of the two motifs conserved among Not proteins of sea urchin and vertebrates. Analysis by in situ hybridization revealed that Not gene expression of ascidians could be categorized into three types: expression likely to be conserved between ascidians and vertebrates, that probably unique to ascidians, and that specific to ascidian species. Expression of ascidian Not in the posterior end of the tail as well as the notochord and a small part of the anterior neural tube at the tailbud stage is reminiscent of the expression of the vertebrate counterparts in the tailbud, which is regarded as a continuation of the organizer and the pineal gland, respectively. The expression of Not in the epidermis precursors during cleavage stage may be unique to ascidians. In the light of the present findings, evolutionary aspects of Not genes are discussed.Electronic Supplementary Material Supplementary material is available for this article at Edited by N. Satoh     

Characterization of the γc chain among 27 unrelated Japanese patients with X-linked severe combined immunodeficiency (X-SCID)

X-linked severe combined immunodeficiency (X-SCID) is a rare fatal disease that is caused by mutations in the gene encoding the gammac chain. In this study, 27 unrelated Japanese patients with X-SCID were examined in terms of their genetic mutations and surface expression of the gammac chain. Among 25 patients examined, excluding two patients with large deletions, 23 different mutations were identified in the IL2RG gene, including 10 novel mutations. One patient bearing an extracellular mutation and all three of the patients bearing intracellular mutations after exon 7 expressed the gammac chain on the cell surface. Overall, 84% of patients lacked surface expression of the gammac chain leading to a diagnosis of X-SCID.     

Temperature-dependent hyper-activation of monoglucosyldiacylglycerol synthase is post-translationally regulated in Synechocystis sp. PCC 6803

The mechanism of monoglucosyldiacylglycerol (MGlcDG) increase following heat shock in Synechocystis sp. PCC 6803 was examined by measuring MGlcDG synthase (Sll1377) activity. Temperature-dependent activation of Sll1377 was observed in the membrane fraction of Synechocystis sp. PCC 6803, whereas the Sll1377 protein level remained unchanged, suggesting that the activity is post-translationally regulated without covalent modification of Sll1377 by soluble enzymes. Four individual mutations introduced into recombinant Sll1377 (D147, D200, R329, and R331) significantly reduced the activity and blocked temperature-dependent activation, suggesting that these amino acid residues are essential for Sll1377 activity at both normal growth temperature and the higher temperature.