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1.
The soluble fraction extracted from Escherichia coli A19 (Hfr, rel met rns) during early and late times of phenotypic and genotypic induced relaxed control have been examined for the possible accumulation of ribosomal proteins (r-proteins) and rRNA species during this time of unbalanced macromolecular synthesis. Ribosomal proteins and rRNA species were not found to accumulate within the soluble fraction at any time during this period of relaxed control; even after the typical rRNA accumulation had ceased, r-proteins did not accumulate. It is concluded, from these and related observations, that the r-proteins and rRNA species known to be produced during relaxation must immediately associate to form the unusual ribonucleoprotein particles (e.g. 'relaxed particles' and 'chloramphenicol particles') characteristic of periods of relaxed control. Since r-proteins do not accumulate even when net RNA accumulation halts, it appears that some elements of the normal, basic co-ordination between rRNA and r-protein synthesis/stability persist even during relaxed control. 相似文献
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J B Rafferty S E Phillips C Rojas G Boulot I Saint-Girons Y Guillou G N Cohen 《Journal of molecular biology》1988,200(1):217-219
The met repressor from Escherichia coli has been crystallized in space group P21, with unit cell dimensions a = 35.6 A, b = 62.6 A, c = 44.5 A, beta = 102.4 degrees and one aporepressor dimer per asymmetric unit. Preliminary X-ray diffraction photographs show measurable intensities to beyond 1.5 A resolution, and the crystal form is ideally suited to high-resolution crystallographic analysis (1 A = 0.1 nm). 相似文献
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The pattern of chromosome replication in an exponentially growing culture of an Hfr strain of Escherichia coli has been compared to that obtained with the same Hfr following a procedure which synchronizes rounds of DNA replication. The results indicate that there is significant replication from the integrated plasmid following the synchronization procedure, whereas in the exponentially growing culture replication starts most frequently from the normal origin with little, if any, replication from the sex factor, F. 相似文献
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The stringent factor extracted from several independently isolated rel- mutants is more thermolabile than the stringent factor extracted from the parental rel+ strain. This thermolability is characteristically different in each of the mutants. This strongly suggests that the stringent factor is the product of the rel gene. 相似文献
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Growth abnormalities in Hfr derivatives of Escherichia coli strain C 总被引:56,自引:0,他引:56
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Isolation and characterisation of Hfr strains from a recombination-deficient strain of Escherichia coli 总被引:6,自引:0,他引:6
Summary A T6s RecA- strain carrying a lac proB deletion and Fts
lac
+ was challenged with phage T6 and survivors which were both T6r and Lac+ at 42° were tested for fertility. Among these were a number of Hfr strains which had their points of origin at or near the tsx locus and which still carried the recA allele. These arose in comparable frequencies in the RecA- strain and in a Rec+ analogue. We conclude that such integration does not require the RecA function. The rate of chromosome transfer was similar in one such RecA- Hfr and its Rec+ derivative; the yield of recombinants from the RecA- strain was slightly lower than from its Rec+ derivative. 相似文献
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Deoxyribonucleic Acid Transferred from Ultraviolet-Irradiated Excision-Defective Hfr Cells of Escherichia coli K-12 总被引:3,自引:3,他引:3
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Deoxyribonucleic acid (DNA) transfer from (3)H-thymine-labeled Hfr cells has been measured by determining the amount of radioactivity remaining after selective lysis of the donor cells in the mating mixture. DNA transfer was less effectively reduced by ultraviolet irradiation of excision-defective Hfr cells than was the yield of recombinants. The buoyant density of DNA transferred from unirradiated and irradiated Hfr cells was equivalent to that of double-stranded DNA. Mating-dependent DNA synthesis in the recipient has been measured by mating Hfr cells deficient in thymidine kinase with irradiated thymine-requiring F(-) cells in the presence of (3)H-thymine. The extent of such DNA synthesis approximated the amount of DNA transferred from unirradiated donors. Neither DNA transfer nor mating-dependent DNA synthesis could be reliably measured when both parents were irradiated. It is proposed that transferred Hfr DNA is replicated in the recipient and that this replication still occurs when the Hfr DNA contains dimers. 相似文献
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The polypeptides present in 35S-labelled chromatin prepared from Escherichia coli cells, and polypeptides present in the DNA and RNA complexes obtained by micrococcal nuclease digestion of the chromatin, were analysed by two-dimensional non-equilibrium polyacrylamide gel electrophoresis. Three hundred and thirty-five 35S-labelled polypeptides were detected in the chromatin whereas the DNA- and RNA-containing fractions of the micrococcal nuclease digest contained 126 and 183 polypeptides respectively. The major basic low-molecular-weight polypeptides were found in the DNA-containing fractions. 相似文献
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Immunological analysis of the heme proteins present in aerobically grown Escherichia coli. 总被引:2,自引:2,他引:2
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Immunological methods were used to obtain information about Escherichia coli heme proteins. There is a membrane-bound catalase which consists of a single subunit (as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis) which is also present in the soluble fraction. Antibodies raised against purified, soluble cytochrome b562 showed that this cytochrome is not related to any of the membrane-bound cytochromes, including the b562 component of the cytochrome o complex. Cytochrome b556 is immunologically unrelated to the cytochrome b556 NR associated with the nitrate reductase system. Cytochrome b556 and cytochrome o are not present in a constant ratio in the membrane. 相似文献
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Close linkage of prd and rel genes in Escherichia coli K-12 总被引:3,自引:0,他引:3
Roy R. B. Russell 《Molecular & general genetics : MGG》1973,124(4):369-370
Summary The prd gene, the mutant allele of which permits growth of E. coli on 1,2-propanediol as sole carbon source, has been located by transduction very close to the rel (RNA control) gene. This close linkage provides a convenient means for the inter-strain transfer of rel.This work was supported in part by the Australian Meat Research Committee. 相似文献
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Matzura H 《FEBS letters》1970,6(1):5-8
Study of the relative proportions of ribosomes and polysomes released by a standardized lysing procedure from isogenic RC(str) and RC(rel) strains of Escherichia coli shows that a 20-min period of amino acid starvation of RC(str) bacteria reduces the fraction of ribosomes recovered in polysomes to about 60% of its value characteristic of exponentially growing cells: A similar starvation treatment of the RC(rel) bacteria causes no appreciable reduction in the fraction of polysomal ribosomes. 相似文献
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The Escherichia coli ATP-binding cassette (ABC) proteins 总被引:7,自引:1,他引:7
The recent completion of the Escherichia coli genome sequence ( Blattner et al ., 1997 ) has permitted an analysis of the complement of genomically encoded ATP-binding cassette (ABC) proteins. A total of 79 ABC proteins makes this the largest paralogous family of proteins in E . coli . These 79 proteins include 97 ABC domains (as some proteins include more than one ABC domain) and are components of 69 independent functional systems (as many systems involve more than one ABC domain). The ABC domains are often, but not exclusively, the energy-generating domains of multicomponent membrane-bound transporters. Thus, 57 of the 69 systems are ABC transporters, of which 44 are periplasmic-binding protein-dependent uptake systems and 13 are presumed exporters. The genes encoding these ABC transporters occupy almost 5% of the genome. Of the 12 systems that are not obviously transport related, the function of only one, the excision repair protein UvrA, is known. A phylogenetic analysis suggests that the majority of ABC proteins can be assigned to 10 subfamilies. Together with statistical and, importantly, biological evidence, this analysis provides insight into the evolution and function of the ABC proteins. 相似文献
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The mechanism of reversible transfer of the gamma-phosphate group of ATP by Escherichia coli phosphoenolpyruvate carboxykinase (PCK) on to its substrate is of great interest. It is known that metallofluorides are accurate analogs of the transition state in the context of kinase mechanisms. Therefore, two complexes of PCK, one with AlF(3), Mg(2+) and ADP (complex I), the other with AlF(3), Mg(2+), ADP and pyruvate (complex II) were crystallized. The X-ray crystal structures of these two complexes were determined at 2.0 A resolution. The Al atom has trigonal bipyramidal geometry that mimics the transition state of phosphoryl transfer. The Al atom is at a distance of 2.8 A and 2.9 A from an oxygen atom of the beta-phosphoryl group of ADP in complex I and II, respectively. A water molecule in complex I and an oxygen atom of the pyruvate in complex II are located along the axis of the trigonal bipyramid on the side opposite to the beta-phosphoryl oxygen with respect to the equatorial plane, suggesting that the complexes are close mimics of the transition state. Along with the presence of positively charged species around the AlF(3) moiety, these results indicate that phosphoryl transfer occurs via a direct displacement mechanism with associative qualities. 相似文献
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Isolation of Circular Deoxyribonucleic Acid from Salmonella typhosa Hybrids Obtained from Matings with Escherichia coli Hfr Donors
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R. W. Leavitt J. A. Wohlhieter E. M. Johnson G. E. Olson L. S. Baron 《Journal of bacteriology》1971,108(3):1357-1365
Heterozygous, partial diploid Salmonella typhosa hybrids obtained from matings with Escherichia coli K-12 Hfr strains were observed to contain supercoiled, circular deoxyribonucleic acid (DNA) when examined by the dye-buoyant density method. Examination of one such S. typhosa hybrid after its loss, by segregation, of the inherited E. coli genetic markers revealed a concurrent loss of its supercoiled circular DNA. Subsequent remating of this segregant with various E. coli Hfr strains resulted in the reappearance of the circular DNA. Molecular weight determinations of circular DNA molecules isolated from a number of S. typhosa partial diploid hybrids were made by sucrose density gradient ultracentrifugation and electron microscopy. These studies revealed a range of molecular sizes among the various hybrids examined, but each hybrid exhibited only a single characteristic size for its contained circular DNA. The range of size is consistent with the presence in each hybrid of a different length of E. coli chromosome. It was concluded that the E. coli Hfr genetic segments transferred to these S. typhosa hybrids were conserved, in the diploid state, in the form of supercoiled, circular DNA molecules. 相似文献