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Selected AbstractsUstilago maydis spermidine synthase is encoded by a chimeric gene, required for morphogenesis, and indispensable for survival in the hostFEMS YEAST RESEARCH, Issue 6 2009Laura Valdés-Santiago Abstract To analyze the role of spermidine in cell growth and differentiation of Ustilago maydis, the gene encoding spermidine synthase (Spe) was isolated using PCR. We found that the enzyme is encoded by a chimeric bifunctional gene (Spe-Sdh) that also encodes saccharopine dehydrogenase (Sdh), an enzyme involved in lysine biosynthesis. The gene contains a 5, region encoding Spe, followed, without a termination signal or a second initiation codon, by a 3, region encoding Sdh, and directs the synthesis of a single transcript that hybridizes with 3, or 5, regions' probes of the gene. The gene could not be disrupted in a wild-type strain, but only in a mutant defective in the gene encoding ornithine decarboxylase (Odc). Single spe-sdh mutants were isolated after sexual recombination in planta with a compatible wild-type strain. Mutants were auxotrophic for lysine and spermidine, but not for putrescine, and contained putrescine and spermidine, but not spermine. Putrescine in double mutants is probably synthesized from spermidine by the concerted action of polyamine acetyl transferase and polyamine oxidase. spe-sdh mutants were sensitive to stress, unable to carry out the yeast-to-mycelium dimorphic transition, and showed attenuated virulence to maize. These phenotypic alterations were reverted by complementation with the wild-type gene. [source] Identification of an operon and inducing peptide involved in the production of lactacin B by Lactobacillus acidophilusJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007A.E. Dobson Abstract Aim: To determine if a 9·5-kb region on the Lactobacillus acidophilus NCFM genome, encoded the genetic determinants for regulation and production of lactacin B, a class II bacteriocin. Methods: Transcriptional analysis was used to identify a 9·5-kb polycistronic region suspected of encoding the lab operon. The 12 putative open reading frames (LBA1803,LBA1791) were organized into three clusters: a production and regulation cluster encoding a putative two-component signal transduction system; an export cluster encoding a putative ABC transporter and a final cluster composed of three unknown proteins. Seven genes were typical of bacteriocins, encoding small, cationic peptides, each with an N-terminal double-glycine leader motif. Inactivation of a predicted ABC transporter completely abolished bacteriocin activity. When cloned and expressed together, LBA1803,LBA1800 resulted in markedly higher levels of lactacin B activity. The four peptides were chemically synthesized but exhibited no bacteriocin activity, alone or in combination. Only LBA1800 induced lactacin B production in broth cultures. Conclusions: Lactacin B production is encoded within the 9·5-kb lab operon of 12 genes that are transcribed in a single transcript. LBA1800 is an inducing peptide of bacteriocin production. Significance and Impact of the Study: A three-component regulatory system common to class II bacteriocins regulates the production of this bacteriocin by Lact. acidophilus. [source] Identification of a novel protein from glial cells based on its ability to interact with NF-,B subunitsrJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2003Thersa Sweet Abstract Nuclear factor ,B (NF-,B) represents a family of inducible DNA-binding transcription factors whose activity is critical for expression of the HIV-1 genome in a broad range of cells. In addition to its interaction with the ,B DNA sequence, the association of NF-,B subunits with other cellular proteins plays an important role in stimulation of HIV-1 gene transcription in astrocytic cells. Here, we utilized a yeast two-hybrid system to screen a cDNA library from a human astrocytic cell line and were able to isolate a partial cDNA belonging to a gene with an open reading frame of 1,871 amino acid residues which binds to both the p50 and p65 subunits of NF-,B. This gene, named NF-,B-binding protein (NFBP) is located on chromosome 10q24.2-25.1 and hybridized to a single transcript of nearly 6 kb in size. It is localized to the nucleus, specifically the nucleolus of cells. Extensive computer analysis was performed with the sequence of the full length NFBP and significant homology was found between NFBP, and yeast and mouse proteins. A discussion of the potential roles of NFBP in normal and viral infected cells is included. © 2003 Wiley-Liss, Inc. [source] The galactokinase of Hypocrea jecorina is essential for cellulase induction by lactose but dispensable for growth on d -galactoseMOLECULAR MICROBIOLOGY, Issue 4 2004Bernhard Seiboth Summary Lactose is the only soluble carbon source which can be used economically for the production of cellulases or heterologous proteins under cellulase expression signals by Hypocrea jecorina (=Trichoderma reesei). Towards an understanding of lactose metabolism and its role in cellulase formation, we have cloned and characterized the gal1 (galactokinase) gene of H. jecorina, which catalyses the first step in d -galactose catabolism. It exhibits a calculated Mr of 57 kDa, and shows moderate identity (about 40%) to its putative homologues of Saccharomyces cerevisiae and Kluyveromyces lactis. Gal1 is a member of the GHMP family, shows conservation of a Gly/Ser rich region involved in ATP binding and of amino acids (Arg 51, Glu 57, Asp 60, Asp 214, Tyr 270) responsible for galactose binding. A single transcript was formed constitutively during the rapid growth phase on all carbon sources investigated and accumulated to about twice this level during growth on d -galactose, l -arabinose and their corresponding polyols. Deletion of gal1 reduces growth on d -galactose but does only slightly affect growth on lactose. This is the result of the operation of a second pathway for d -galactose catabolism, which involves galactitol as an intermediate, and whose transient concentration is strongly enhanced in the delta- gal1 strain. In this pathway, galactitol is catabolised by the lad1 -encoded l -arabinitol-4-dehydrogenase, because a gal1/lad1 double delta-mutant failed to grow on d -galactose. In the delta- gal1 strain, induction of the Leloir pathway gene gal7 (encoding galactose-1-phosphate uridylyltransferase) by d -galactose, but not by l -arabinose, is impaired. Induction of cellulase gene expression by lactose is also impaired in a gal1 deleted strain, whereas their induction by sophorose (the putative cellulose-derived inducer) was shown to be normal, thus demonstrating that galactokinase is a key enzyme for cellulase induction during growth on lactose, and that induction by lactose and sophorose involves different mechanisms. [source] | ||||||||||