Biomedical subjects

J F García-Bustos

Publications and source records attributed to J F García-Bustos.

6 recordsLinked to original sources

PubMed2001

Annotated draft genomic sequence from a Streptococcus pneumoniae type 19F clinical isolate.

The public availability of numerous microbial genomes is enabling the analysis of bacterial biology in great detail and with an unprecedented, organism-wide and taxon-wide, broad scope. Streptococcus pneumoniae is one of the most important bacterial pathogens throughout the world. We present here sequences and functional annotations for 2.1-Mbp of pneumococcal DNA, covering more than 90% of the total estimated size of the genome. The sequenced strain is a clinical isolate resistant to macrolides and tetracycline. It carries a type 19F capsular locus, but multilocus sequence typing for several conserved genetic loci suggests that the strain sequenced belongs to a pneumococcal lineage that most often expresses a serotype 15 capsular polysaccharide. A total of 2,046 putative open reading frames (ORFs) longer than 100 amino acids were identified (average of 1,009 bp per ORF), including all described two-component systems and aminoacyl tRNA synthetases. Comparisons to other complete, or nearly complete, bacterial genomes were made and are presented in a graphical form for all the predicted proteins.

DNA, Bacterial↗

PubMed2000

Nitric oxide-producing CD11b(+)Ly-6G(Gr-1)(+)CD31(ER-MP12)(+) cells in the spleen of cyclophosphamide-treated mice: implications for T-cell responses in immunosuppressed mice.

During recovery from intensive chemotherapy with cyclophosphamide (CTX), mice suffer a severe but transitory impairment in spleen cell proliferation to T-cell mitogens (Con A or anti-CD3 plus IL-2). Although CTX treatment reduced spleen T-cell cellularity, this cannot fully account for T-cell unresponsiveness. The results showed that CTX induces the colonization of spleen by an immature myeloid CD11b(+)Ly-6G(+)CD31(+) population. Its presence closely correlated with the maximum inhibition of T-cell proliferation. Moreover, this suppressive activity was dependent on nitric oxide (NO) production in cultures since (1) higher amounts of nitric oxide and inducible nitric oxide synthase (iNOS) mRNA were produced in CTX spleen cells (CTX-SC) than in control splenocyte cultures and (2) NOS inhibitors greatly improved the proliferation of T lymphocytes. Nitric oxide production and suppressive activity were also dependent on endogenous interferon-gamma (IFN-gamma) production since anti-IFN-gamma abrogated both effects. Finally, iNOS protein expression was restricted to a heterogeneous population of CD31(+) cells in which CD11b(+)Ly-6G(+) cells were required to suppress T-cell proliferation. These results indicated that CTX might also cause immunosuppression by a mechanism involving the presence of immature myeloid cells with suppressor activity. This may have implications in clinical praxis since inappropriate immunotherapies in patients treated with intensive chemotherapy could lead to deleterious T-cell responses. (Blood. 2000;95:212-220)

Animals↗

PubMed1999

Translation elongation factor 2 is encoded by a single essential gene in Candida albicans.

Translation elongation factor 2 (eEF2) is a large protein of more than 800 amino acids which establishes complex interactions with the ribosome in order to catalyze the conformational changes needed for translation elongation. Unlike other yeasts, the pathogenic fungus Candida albicans was found to have a single gene encoding this factor per haploid genome, located on chromosome 2. Expression of this locus is essential for vegetative growth, as evidenced by placing it under the control of a repressible promoter. This C. albicans gene, named EFT2, was cloned and sequenced (EMBL accession number Y09664). Genomic and cDNA sequence analysis identified common transcription initiation and termination signals and an 842 amino acid open reading frame (ORF), which is interrupted by a single intron. Despite some genetic differences, CaEFT2 was capable of complementing a Saccharomyces cerevisiae Deltaeft1 Deltaeft2 null mutant, which lacks endogenous eEF2, indicating that CaEFT2 can be expressed from its own promoter and its intron can be correctly spliced in S. cerevisiae.

Candida albicans↗

PubMed1998

Ribosomal P-protein stalk function is targeted by sordarin antifungals.

Sordarin derivatives are remarkably selective inhibitors of fungal protein synthesis. Available evidence points to a binding site for these inhibitors on elongation factor 2, but high affinity binding requires the presence of ribosomes. The gene mutated in one of the two isolated complementation groups of Saccharomyces cerevisiae mutants resistant to the sordarin derivative GM193663 has now been identified. It is RPP0, encoding the essential protein of the large ribosomal subunit stalk rpP0. Resistant mutants are found to retain most of the binding capacity for the drug, indicating that mutations in rpP0 endow the ribosome with the capacity to perform translation elongation in the presence of the inhibitor. Other proteins of the ribosomal stalk influence the expression of resistance, pointing to a wealth of interactions between stalk components and elongation factors. The involvement of multiple elements of the translation machinery in the mode of action of sordarin antifungals may explain the large selectivity of these compounds, even though the individual target components are highly conserved proteins.

Amino Acid Sequence↗

PubMed1998

Translation elongation factor 2 is part of the target for a new family of antifungals.

Translation elongation factor 2 (EF2), which in Saccharomyces cerevisiae is expressed from the EFT1 and EFT2 genes, has been found to be targeted by a new family of highly specific antifungal compounds derived from the natural product sordarin. Two complementation groups of mutants resistant to the semisynthetic sordarin derivative GM193663 were found. The major one (21 members) consisted of isolates with mutations on EFT2. The minor one (four isolates) is currently being characterized but it is already known that resistance in this group is not due to mutations on EFT1, pointing to the complex structure of the functional target for these compounds. Mutations on EF2 clustered, forming a possible drug binding pocket on a three-dimensional model of EF2, and mutant cell extracts lost the capacity to bind to the inhibitors. This new family of antifungals holds the promise to be a much needed and potent addition to current antimicrobial treatments, as well as a useful tool for dissection of the elongation process in ribosomal protein synthesis.

Amino Acid Sequence↗

PubMed1984

Microcin 7: purification and properties.

Microcin 7 is an antibiotic peptide, produced and excreted to the culture medium by E. coli strains harboring the plasmid pRYC7. This peptide was extracted from the culture media by adsorbing it on octadecyl silica. It was purified by gel filtration on Sephadex G-25 and reverse phase high performance liquid chromatography. Its amino acid composition is the following: Ala (0.8), Arg (1.9), Asx (1.9), Gly (1.5), Met (0.8) and Thr (0.9). The purified peptide dose not react with ninhydrin and it is resistant to carboxypeptidase degradation, indicating that the molecule may be a cyclic or end-blocked oligopeptide.

Amino Acids↗