RESUMO
The rolC gene of Agrobacterium rhizogenes codes for a peptide with an apparent molecular weight of approximately 20 kDa. Immunolocalization of the rolC peptide, in leaves of transgenic plants which are genetic mosaics for the expression of the rolC gene, is restricted to the phenotypically altered sectors. Subcellular fractionation of homogenates from 35S-rolC transgenic leaves shows the cytosolic localization of the rolC peptide.
Assuntos
Proteínas de Bactérias/genética , Nicotiana/genética , Plantas Tóxicas , Rhizobium/genética , Animais , Proteínas de Bactérias/análise , Clonagem Molecular , Citosol/metabolismo , Técnicas Imunológicas , Coelhos , Nicotiana/análiseRESUMO
The localization of plasma membrane H(+)-ATPase has been studied at the optical microscope level utilizing frozen and paraffin sections of Avena sativa and Pisum sativum, specific anti-ATPase polyclonal antibody, and second antibody coupled to alkaline phosphatase. In leaves and stems the ATPase is concentrated at the phloem, supporting the notion that it generates the driving force for phloem loading. In roots the ATPase is concentrated at both the periphery (rootcap and epidermis) and at the central cylinder, including endodermis and vascular cells. This supports a ;two-pump' mechanism for ion absorption, involving active uptake at the epidermis, symplast transport across the cortex, and active efflux at the xylem. The low ATPase content of root meristem and elongation zone may explain the observed transorgan H(+) currents, which leave nongrowing parts and enter growing tips.
RESUMO
Gene SUC4 produced about four fold more invertase activity than did gene SUC5. However, these genes differ in only three positions located in the 5' non-coding region. The difference in gene expression between SUC4 and SUC5 must be due to the G to A transition (position-497) and/or the C to T transition (position -460) in the upstream activator sequences. The sequence TACAAA present in SUC5 can play the same role than the TATAAA box of SUC4.
Assuntos
Regulação da Expressão Gênica , Genes Fúngicos , Glicosídeo Hidrolases/genética , Saccharomyces cerevisiae/genética , Adenosina/genética , Sequência de Bases , DNA Fúngico/genética , DNA Recombinante , Guanosina/genética , Saccharomyces cerevisiae/enzimologia , Transformação Genética , beta-FrutofuranosidaseRESUMO
mRNAs from reticulocyte polysomes were fractionated by chromatography on poly(U)-Sepharose and thermal elution. The molar ratio of alpha- to beta-globin mRNA was found to be 2:1 and 1:1 respectively in short- and long-poly(A) size classes. Translational analyses indicated that the globin mRNAs containing long poly(A) tracts (with a mean length of about 70 nucleotides) directed protein synthesis with higher rates than did mRNA containing short poly(A) tracts (15-35 nucleotides). Experiments performed with sub-saturating mRNA concentrations showed that the digestion with RNAase H induced a decrease in the translational capacity of both globin mRNAs and an increase in the alpha- to beta-globin synthesis ratio. No correlation was observed between the size of the poly(A) tail in mRNA and the optimal K+ requirement for translation.
Assuntos
Globinas/genética , Poli A/análise , Biossíntese de Proteínas , RNA Mensageiro/genética , Sequência de Bases , Cromatografia de Afinidade , DNA/genética , Eletroforese em Gel de Poliacrilamida , Globinas/biossíntese , Dados de Sequência Molecular , Potássio/farmacologia , Biossíntese de Proteínas/efeitos dos fármacosRESUMO
The relative rates of initiation of alpha- and beta-globin mRNA translation in a Krebs II ascites cell-free system are differently modulated by a 50-kDa protein and two fractions containing either a 28-kDa or a 24-kDa polypeptide. Each of these fractions stimulated a discrete step that limits initiation of protein synthesis, but other rate-limiting steps take place upstream and/or downstream, resulting in characteristic kinetics of the stimulation of alpha- and beta-globin synthesis. The ascites extracts appear to be deficient in these activities.
