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191.
192.
Purification and characterization of a low molecular weight transforming growth factor from the urine of melanoma patients 总被引:1,自引:0,他引:1
A low Mr human transforming growth factor (TGF) present in melanoma patients' urine has been purified approximately 200,000-fold to apparent homogeneity. Initial purification of an acid-soluble fraction of urine was achieved by Bio-Gel P-30 gel filtration chromatography in 1 M acetic acid. TGF activities were demonstrated in the Mr ranges of 30,000 and 6,000-10,000. These competed with epidermal growth factor (EGF) for binding to A431 membrane receptors and induced anchorage-independent growth of untransformed fibroblasts. The low Mr TGF activity obtained from P-30 chromatography was purified to apparent homogeneity by two sequential reverse-phase high performance liquid chromatography steps with a mu Bondapak C18 column first using a linear gradient of acetonitrile going from 0-60% in 120 min and then by rechromatography of the activity over the same column using a shallower gradient of acetonitrile going from 20-40% in 160 min. The isoelectric point of the melanoma patient-derived urinary TGF was determined to be 6.2, which is distinct from that for human EGF. Amino acid composition analysis of the purified urinary TGF (uTGF) revealed that it is composed of at least 42 amino acid residues with a minimum estimated Mr of 4,545. Compositional analysis further revealed distinct similarities and differences between the uTGF, human EGF and TGFs secreted by various transformed human and rodent cell lines. 相似文献
193.
Gwang Hoon Gil Seung Rim Kim Jong Chan Bae Jae Heung Lee 《Enzyme and microbial technology》1985,7(8):370-372
Effects of inoculum size and total sugar content on both l-phenylalanine productivity and titre have been investigated using a tyrosine auxotrophic regulatory mutant of Escherichia coli. Fermentations were carried out in a 500 litre pilot fermenter with intermittent feeding of d-glucose plus phosphate. It was found that the productivity was not greatly affected by inoculum size. However, the l-phenylalanine titre was significantly affected by total sugar content. Relatively high productivities of up to 0.35–0.40 g l-phenylalanine l?1 h?1 have been achieved at l-phenylalanine titres of 14–15 g l?1. 相似文献
194.
Abstract Isolation of plasmid DNA followed by plasmid curing was carried out to examine the relationship of plasmid to carbon monoxide dehydrogenase (CO-DH) production in carboxydobacteria. A small plasmid of almost identical size (1.52−1.76 × 106 ) was present in Pseudomonas carboxydovorans, Azotobacter sp.1, and Azomonas sp.2. Azomonas sp.1 contained two kinds of plasmids (1.5 × 106 and 2.47 × 106 ). No plasmids were found in Pseudomonas carboxydohydrogena , JC1, and HY1. A plasmid-cured clone of P. carboxydovorans was obtained by growing the cells at 37°C. The cured cell was able to grow CO autotrophically on solid, but not in liquid, medium. CO-DH of the cured cell was active and consisted of three subunits similar to those found in the wild-type enzyme, with the exception that the β subunit of the enzyme was larger than that of the wild-type enzyme. These results suggest that the small plasmids do not carry genes encoding CO-DH but may have gene(s) for processing the β subunit of the enzyme. 相似文献
195.
In studying plasmid instability in recombinant microorganisms, Escherichia coli MV 12[p VH5] and MV 12 trpR[p VH5] harboring trp operon were used as experimental model systems. The host with the trp repression system was partially derepressed by 3-beta-indoleacrylic acid. The results from kinetic analysis of plasmid instability showed that the stability of p VH5 and the growth rate of MV 12[p VH5] decreased rapidly in presence of 3-beta-indoleacrylic acid at a concentration higher than 10 mug/mL, but beyond 30 g/mL no significant change was observed. This suggests that Trp(-) variants from MV 12[p VH5] could be produced from the host cells at a different frequency depending on the physiological condition. In another system, MV 12 trpR[p VH5] which was constructed by conjugation of E. coli MV 12[p VH5] with E. coli CSH61, the plasmid stability was much lower and the frequency of Trp(-) cell production was about 10 times higher as compared with the MV 12[p VH5] when treated with 3-beta-indoleacrylic acid. A kinetic model representing the plasmid instability was derived, and a fairly good agreement with the experimental results was found. The fraction of plasmid-free cell (or negative variant) shows a different time course profile depending on the segregation coefficient (a, production rate of negative variants from positive cells during one generation), growth ratio (G, the ratio of growth rates of negative variants to positive cells), and other parameters. The negative variant fraction continues to increase ("run away" type) or it approaches to a finite value ("settling" type) depending on the relative values of a and G. 相似文献
196.
Nonoccluded baculovirus-and filamentous virus-like particles were found in nuclei of hemocytes or midgut cells of field-collected spotted cucumber beetles. Each type of particle was associated with a different type of virogenic stroma containing various viral components similar to those referred to as capsid, nucleocapsid, viroplasm, and viral envelope in other known baculovirus infections. Nucleocapsids of the virus which occured only in hemocytes were rod-shaped particles approximately 230 nm long and 52 nm wide and were enveloped singly by a trilaminar unit membrane. Enveloped and partly enveloped particles appeared to be released from the nucleus to the cytoplasm by budding through the nuclear envelope acquiring additional membranes. The nucleocapsids of the virus which occurred only in nuclei of midgut cells were filamentous particles with an average diameter of 25 nm and variable length up to 2 μm. Some extremely long particles were bent almost 360° near the middle, resulting in a hairpin-like configuration. The particles were always enveloped singly. No particles budding through the nuclear envelope were observed. 相似文献
197.
Intact or hypophysectomized 23-day-old hamsters and rats were injected s.c. with 2 mg diethylstilboestrol (DES) or 1 mg oestradiol cyclopentylpropionate (OECP) on Days 23-25 and killed on Day 26. Although serum oestradiol was elevated to the same high levels by OECP, ovarian and uterine weights were increased in the rat by OECP or DES whereas only the uterus responded in the hamster. This correlated with the ability of the oestrogens to increase significantly the number of large preantral and antral follicles in the intact rat but only the number of follicles with 2-3 layers of granulosa cells in the immature hamster. Qualitative study revealed that DES and OECP increased the number of large preantral follicles in the adult hypophysectomized rat but were ineffective in the adult hamster. It is concluded that for the immature and adult hamster oestrogens do not play a major role in the recruitment of large preantral follicles. 相似文献
198.
Summary Additon of pyruvate or leucine was found to be efficient for increasing the intracellular ratios of NADH/NAD and NADPH/NADP while reducing the coenzyme A concentration during the cultivation of Alcaligenes eutrophus. Poly--hydroxybutyrate (PHB) accumulation was enhanced more than 2-fold since metabolic flux of acetyl-CoA into PHB synthetic pathway could be facilitated by the changes of the cofactor concentrations. 相似文献
199.
Inactivation of 3 alpha-hydroxysteroid dehydrogenase by superoxide radicals. Modification of histidine and cysteine residues causes the conformational change. 下载免费PDF全文
3 alpha-Hydroxysteroid dehydrogenase (EC 1.1.1.50) from Pseudomonas testosterone was inactivated by superoxide radicals generated by the aerobic xanthine oxidase reaction. Superoxide dismutase, NAD+, bovine serum albumin and histidine and cysteine as free amino acids partially protected the enzyme from inactivation. NADH-binding properties were determined by fluorescence spectroscopy, and no variation was found between native enzyme and the unmodified fraction of the partly inactivated one. The fluorescence emission maximum for the completely inactivated enzyme was shifted 10 nm to a longer wavelength when compared with the native one, and it seems possible that the modification of histidine and cysteine residues by superoxide radicals causes the conformational change of the enzyme and the consequent loss of catalytic activity. 相似文献
200.
Partial purification of a nuclear protein that binds to the CCAAT box of the mouse alpha 1-globin gene. 总被引:32,自引:16,他引:16 下载免费PDF全文
We enriched a fraction from nuclear extracts of murine erythroleukemia cells which contains a protein able to form stable complexes with the promoter region of the alpha 1-globin gene. Binding activity, which is present in mouse brain and a variety of cultured mouse and human cell lines, is not erythroid cell specific. Binding studies with alpha-globin gene promoter deletion mutants as well as DNase I footprinting and dimethyl sulfate protection studies showed that the factor bound specifically to the CCAAT box of the alpha 1 promoter. Enriched factor preparations exhibited weak binding to the promoter region of the beta maj-globin gene. This suggests that this protein could bind differentially to these two promoters in vivo. The enriched factor may be a ubiquitous nuclear protein involved in the differential regulation of the alpha 1- and beta maj-globin genes. 相似文献