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  • Key words: Yeast — Slippage — Amino acid tandem repeats — Homopeptides — Protein function — Genome analysis — Codon composition  (1)
  • freeze-thawing  (1)
  • 1
    ISSN: 1432-1432
    Schlagwort(e): Key words: Yeast — Slippage — Amino acid tandem repeats — Homopeptides — Protein function — Genome analysis — Codon composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract. Long amino acid repeats are often observed in eukaryotic proteins. In humans, several neurological disorders are caused by proteins containing abnormally long polyglutamines. However, no systematic analysis has attempted to investigate the relationship between reiterations of particular amino acids and protein function, the possible mechanisms involved in the generation of these regions, or the contribution of selection in restricting their genomic distribution, in a large collection of wild-type proteins. We have used baker's yeast open reading frames to study these questions. The most abundant amino acid repeats found in yeast proteins are repeats of glutamine, asparagine, aspartic acid, glutamic acid, and serine. Different amino acid repeats are concentrated in different classes of proteins. Acidic and polar amino acid repeats are significantly associated with transcription factors and protein kinases, while serine repeats are significantly associated with membrane transporter proteins. In most cases the codon structures encoding the repeats at the gene level show a significant bias toward long tracts of one of the possible codons, suggesting that trinucleotide slippage has played an important role in generating these reiterations. However, many, particularly those encoding serine repeats, do not show evidence of slippage. The distributions of codon repeats within proteins and between coding and noncoding regions of the genome, and of amino acids between proteins with different functions, suggest that repeats of these kinds are subject to strong selection.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-6903
    Schlagwort(e): GABAA receptor ; barbiturates ; neurosteroids ; freeze-thawing ; chick optic lobe ; endogenous factors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Studies were carried out to determine whether barbiturates and neurosteroids share common recognition sites at the GABAA receptor complex in avian CNS. To achieve this, differentially prepared fresh and frozen synaptic membranes were used. Both the barbiturate, pentobarbital, and the neurosteroid, 3α-hydroxy-5α-pregnan-20-one, were able to stimulate GABA binding in both types of membranes. Stimulation differed markedly when both drugs were added jointly to different treated tissue. In frozen membranes drugs acted synergistically and were differentially displaced by picrotoxinin, while in fresh ones, where both compounds were inhibited by the convulsant, this additivity was absent. Post-freezing wash supernatants were collected and used as a source of putative endogenous factors involved in the above mentioned membrane differences. Addition of a high molecular weight fraction from supernatants to frozen synaptic membranes led to an inhibition of barbiturate and neurosteroid potentiation, as well as a loss of their additive effect. Our results indicate that GABAA receptor modulation by barbiturates and neurosteroids is affected by synaptic membrane treatment, with a common modulatory site in fresh membranes and separate recognition sites after a freeze-thawing procedure. There may also be endogenous factors involved in overlapping of modulatory sites, which would thus regulate GABAA receptor functionality by direct interaction with the complex.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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