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Phage T4 gene 32 protein and Escherichia coli RNA polymerase were bound to hamster papovavirus DNA. The binding regions were identified by electron microscopy employing a protein-free spreading technique. After gene 32 protein treatment four denaturation regions could be mapped, at 0.04–0.12, 0.30–0.36, 0.50–0.60 and 0.75–0.90 DNA map units, respectively, using the unique BamHI cleavage site as zero point. Eight RNA polymerase binding sites can be found which are localized at positions 0.05; 0.11; 0.18; 0.31; 0.57; 0.66; 0.76 and 0.82. A comparison of the RNA polymerase binding sites with the gene 32 protein denaturation pattern reveals a correspondence of six of eight polymerase binding sites with (A + T)-rich regions within the hamster papovavirus genome.  相似文献   

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A 302 bp DNA fragment and a 113 bp subfragment of the former, both containing the fd gene VIII promoter (P VIII), were found to exhibit temperature-dependent differential behaviour in RNA chain initiation from P VIII. At 37°C no significant differences were observed, while at 17°C chain initiation was strongly suppressed only with the 113 bp fragment. This phenomenon depended on the presence of the (blunt) DNA terminus upstream from P VIII (position −70). Footprinting revealed that at 17°C RNA polymerase was bound to this DNA fragment in a different mode. Contacts were observed only upstream from position −25. On the contrary, at 37°C only the promoter complex footprint was visible. These results indicate that at 17°C formation of the non-initiating complex is more favourable than formation of the promoter complex (which is closed at 17°C; Hofer, B., Müller, D. and Köster, H. (1985) Nucleic Acids Res. 13, 5995–6013) and that formation of both complexes is mutually exclusive. No footprints of RNA polymerase were observed at other DNA termini. This indicates a sequence-specificity for the interaction at the terminus of the 113 bp fragment. The footprint pattern, together with features of the DNA sequence, suggests that the contacts involved in this interaction are similar to those promoter contacts formed upstream from position −20 and that DNA without a −10 region can be specifically recognized by RNA polymerase.  相似文献   

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The number of proline residues in a protein should have very marked consequences for the rates of protein unfolding and refolding according to the model proposed by Brandts et al. (1975). Kinetic simulations of this model indicate that the half-time for refolding of a polypeptide chain with 20 proline residues should be greater than 10 minutes and should increase by about an order of magnitude for each additional 10 proline residues. Various means are considered by which the rate of protein folding in vivo and in vitro might be increased.  相似文献   

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