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1.
Receptor-binding and down-regulatory properties of 22000-Mr human growth hormone and its natural 20000-Mr variant on IM-9 human lymphocytes. 总被引:2,自引:0,他引:2
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Our earlier binding studies of the 22000- and 20000-Mr variants of human growth hormone (somatotropin) to pregnant-rabbit liver and mammary receptors [Closset, Smal, Gomez & Hennen (1983) Biochem. J. 214, 885-892] suggested that the 20000-Mr variant was a lower-affinity analogue of the 22000-Mr molecule. Since the receptor population in these tissues is not fully characterized, we have now investigated the binding of both variants to the well-characterized and highly specific human-growth-hormone receptor of the human lymphocyte IM-9 cell line. The maximum bindability of radioiodinated 22000- and 22000-Mr to IM-9 cells was 60 and 45% respectively. Both hormone variants have essentially the same binding characteristics: slow association (equilibrium reached in 8-10h at 30 degrees C), poor reversibility ('tight binding'), linear Scatchard plot, same specificity as shown by lack of competition by bovine, porcine or equine growth hormones or human growth hormone-(32-46)-(missing in the 20000-Mr variant),-(1-134)- and -(141-191)-peptides. Both unlabelled hormones inhibit binding of both tracers completely, with the 20000-Mr variant being only half as potent as the 22000-Mr one. The apparent affinity is 2.8 X 10(9)M-1 for the 22000-Mr variant and 1.6 X 10(9)M-1 for the 20000-Mr variant. This decreased affinity of the 20000-Mr variant appears to be due to a lower association rate constant. Concentrations (5 ng/ml) of the two variants that occupy about 15% of the total sites induce a marked down-regulation of the receptors after 18h incubation, but the 20000-Mr variant (50% decrease) has a smaller effect than the 22000-Mr variant (75% decrease). Thus the only consequence of the residues-32-46 deletion in the 20000-Mr variant is a lower association rate and affinity for the IM-9 lymphocyte human-growth-hormone receptor. The close binding characteristics of the two forms suggest that the known differences in their insulin-like effects cannot be explained by differences in the nature of their interaction with the human-growth-hormone receptor. 相似文献
2.
Purification of the 22000- and 20000-mol.wt. forms of human somatotropin and characterization of their binding to liver and mammary binding sites. 总被引:2,自引:1,他引:1
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Quantitative data concerning the binding of 22000-mol.wt. human somatotropin and its 20000-mol.wt. variant are described using pregnant-rabbit liver and mammary-gland receptors. The purification and the complete chemical characterization of both human somatotropin and its 20000-mol.wt. variant is also presented. Contamination of the 20000-mol.wt.-variant preparation by 22000-mol.wt. hormone was found to be 0.5% by weight as measured in radioimmunoassay using monoclonal antibody. Labelling of human somatotropin and its 20000-mol.wt. variant using the Iodogen method is described as well as the characterization of the binding to pregnant-rabbit liver and mammary-gland receptor preparations. The maximum binding capacity of the 125I-labelled human somatotropin was between 50 and 60% to liver particulate receptor, whereas that of the 20000-mol.wt. variant was 30%. The specificity of binding of both forms to rabbit hepatic and mammary-gland receptor was found to be similar for both proteins in the same system. The affinity constants and capacity were respectively 0.7 X 10(10)M-1 and 815 fmol/mg of protein for human somatotropin and 0.6 X 10(10)M-1 and 1.250 fmol/mg of protein for the 20000-mol.wt. variant. These data suggest that both proteins behave as partial agonists to the receptors studied. 相似文献
3.
Cardiac lactate dehydrogenase from the hemoglobin- and myoglobin-free antarctic icefish has been purified by affinity chromatography. Structural and kinetic properties of the enzyme were found close or identical to those of its skeletal muscle counterpart and other M-type lactate dehydrogenases. A model involving a dual oxidative-anaerobic metabolism of the icefish heart is proposed. 相似文献
4.
Populations of Wood mice Apodemus sylvaticus and Bank voles Clelhrionomys glareolus were studied by mark-recapture techniques in five different woodlands but concentrated on an oak Quercus petraea wood and a yew Taxus baccata wood, where food supply was also investigated. Much of the yew wood was on limestone pavement which was greatly creviced thus providing static and quantifiable cover. Indices of the intensity with which food was being searched for were obtained on all areas by seed-removal experiments.
Trappability varied within the populations and seasonally, being highest in summer. Unusually high densities of mice were recorded in the yew wood but not elsewhere; vole densities were always low. There was an inverse relationship between range length and density: mean range length in the yew wood was exceptionally low. Males generally ranged further than females, voles further than mice. Females outnumbered males in the oak wood, where cover was minimal, when the population was low. In the two areas with most cover, males outnumbered females. In a further area, where numbers were initially exceedingly low, the population consisted entirely of males for almost a year. Sexes differed in habitat preference but numbers, especially of males, were significantly correlated with cover. Voles usually bred for shorter periods than mice. Overwinter breeding and increased overwinter survival followed good seed years. Individuals recruited when food was plentiful lived longest. In seed-removal experiments rate of removal increased with shortage of natural seed.
Food and intraspecific aggression were the probable major factors in regulating population size, of mice at least. Cover probably modifies intrinsic mechanisms by reducing numbers of encounters between individuals. 相似文献
Trappability varied within the populations and seasonally, being highest in summer. Unusually high densities of mice were recorded in the yew wood but not elsewhere; vole densities were always low. There was an inverse relationship between range length and density: mean range length in the yew wood was exceptionally low. Males generally ranged further than females, voles further than mice. Females outnumbered males in the oak wood, where cover was minimal, when the population was low. In the two areas with most cover, males outnumbered females. In a further area, where numbers were initially exceedingly low, the population consisted entirely of males for almost a year. Sexes differed in habitat preference but numbers, especially of males, were significantly correlated with cover. Voles usually bred for shorter periods than mice. Overwinter breeding and increased overwinter survival followed good seed years. Individuals recruited when food was plentiful lived longest. In seed-removal experiments rate of removal increased with shortage of natural seed.
Food and intraspecific aggression were the probable major factors in regulating population size, of mice at least. Cover probably modifies intrinsic mechanisms by reducing numbers of encounters between individuals. 相似文献
5.
Ihor R. Lemischka Stephen Farmer Vincent R. Racaniello Phillip A. Sharp 《Journal of molecular biology》1981,151(1):101-120
Bacterial clones containing complementary DNA sequences specific for rat brain α-tubulin messenger RNA were constructed. One plasmid, pILαTl, contains >95% of the sequences found in the mRNA: the entire coding sequence as well as extensive 5′ and 3′ untranslated sequences. Comparison of the rat amino acid sequence with the known chicken α-tubulin sequence (Valenzuela et al., 1981) reveals the extraordinary evolutionary stability of α-tubulin protein. The presence of only two interspecies amino acid differences within analogous 411 amino acid sequences predicts that amino acid substitutions in this protein are fixed with a unit evolutionary period (Wilson et al., 1977) of 550 million years (i.e. the time required for a 1% difference to arise within a specific protein in two diverging evolutionary lineages). An analysis of the silent nucleotide differences, permissible because of the degeneracy of the genetic code, demonstrates that these might not occur in a random fashion. The high guanine-cytosine bias in silent codon positions within the chicken α-tubulin sequence, previously noted by Valenzuela et al. (1981), is not conserved within the rat sequence. This decrease in guanine-cytosine bias is accompanied by a selective loss of CpG dinucleotides in the rat sequence. 相似文献
6.
Interaction of hematopoietic stem cells (HSCs) with their particular microenvironment, or niche, is critical for adult hematopoiesis in the bone marrow (BM). Arai et al. (this issue of Cell) demonstrate that HSCs that express the receptor tyrosine kinase Tie2 are quiescent. Ang-1, the ligand for Tie2, enhanced the ability of HSCs to become quiescent and also induced their adhesion to bone, protecting them from stresses that suppress hematopoiesis. These data suggest that the Ang-1/Tie2 signaling pathway plays a crucial role in the maintenance of HSCs in a quiescent state in the BM niche. 相似文献
7.
Jeffery C. Hanvey Elma Smal Robert J. Suhadolnik David C. Baker 《Nucleosides, nucleotides & nucleic acids》2013,32(1-2):495-496
Abstract Studies on t h e biosynthesis o f the N-nucleoside antibiotics have established that the purine and pyrimidine nucleosides/nucleotides serve as the carbon and nitrogen skeleton, whereas with the C-nucleoside antibioticus, the C-N precursor forthe aglycon is either acetate or glutamate. With the pyrrolopyrimidine nucleoside antibiotics (toyocamycin, tubercidin, and sangi vamycin), either two or three carbons of the N-riboside/ribotide of GTP contribute to carbons 5 and 6 of the pyrrolering and the cyano or carboxamide group. With the naturally occurring nucleoside antibiotic containing the 1,3-diazepine seven-membered ring,2′-deoxycoformycin (dCF)(I), the precursor is not immediately obvious. 相似文献
8.
9.
Oleh V. Lushchak Dmytro V. Gospodaryov Ihor S. Yurkevych Kenneth B. Storey 《Archives of insect biochemistry and physiology》2016,91(1):52-63
Aging is often associated with accumulation of oxidative damage in proteins and lipids. However, some studies do not support this view, raising the question of whether high levels of oxidative damage are associated with lifespan. In the current investigation, Drosophila melanogaster flies were kept on diets with 2 or 10% of either glucose or fructose. The lifespan, fecundity, and feeding as well as amounts of protein carbonyls (PC) and lipid peroxides (LOOH), activities of superoxide dismutase (SOD), catalase, glutathione‐S‐transferase (GST), and glutathione reductase activity of thioredoxin reductase (TrxR) were measured in “young” (10‐day old) and “aged” (50‐day old) flies. Flies maintained on diets with 10% carbohydrate lived longer than those on the 2% diets. However, neither lifespan nor fecundity was affected by the type of carbohydrate. The amount of PC was unaffected by diet and age, whereas flies fed on diets with 10% carbohydrate had about fivefold higher amounts of LOOH compared to flies maintained on the 2% carbohydrate diets. Catalase activity was significantly lower in flies fed on diets with 10% carbohydrates compared to flies on 2% carbohydrate diets. The activities of SOD, GST, and TrxR were not affected by the diet or age of the flies. The higher levels of LOOH in flies maintained on 10% carbohydrate did not reduce their lifespan, from which we infer that oxidative damage to only one class of biomolecules, particularly lipids, is not sufficient to influence lifespan. 相似文献
10.
shRNA knockdown of Bmi-1 reveals a critical role for p21-Rb pathway in NSC self-renewal during development 总被引:7,自引:0,他引:7
Knockout studies have shown that the polycomb gene Bmi-1 is important for postnatal, but not embryonic, neural stem cell (NSC) self-renewal and have identified the cell-cycle inhibitors p16/p19 as molecular targets. Here, using lentiviral-delivered shRNAs in vitro and in vivo, we determined that Bmi-1 is also important for NSC self-renewal in the embryo. We found that neural progenitors depend increasingly on Bmi-1 for proliferation as development proceeds from embryonic through adult stages. Acute shRNA-mediated Bmi-1 reduction causes defects in embryonic and adult NSC proliferation and self-renewal that, unexpectedly, are mediated by a different cell-cycle inhibitor, p21. Gene array analyses revealed developmental differences in Bmi-1-controlled expression of genes in the p21-Rb cell cycle regulatory pathway. Our data therefore implicate p21 as an important Bmi-1 target in NSCs, potentially with stage-related differences. Understanding stage-related mechanisms underlying NSC self-renewal has important implications for development of stem cell-based therapies. 相似文献