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排序方式: 共有52条查询结果,搜索用时 15 毫秒
1.
Complete secretion of activable bovine prochymosin by genetically engineered L forms of Proteus mirabilis. 总被引:1,自引:0,他引:1
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To circumvent problems encountered in the synthesis of active chymosin in a number of bacteria and fungi, a recombinant DNA L-form expression system that directed the complete secretion of fully activable prochymosin into the extracellular culture medium was developed. The expression plasmid constructions involved the in-frame fusion of prochymosin cDNA minus codons 1 to 4 to streptococcal pyrogenic exotoxin type A gene (speA') sequences, including the speA promoter, ribosomal binding site, and signal sequence and five codons of mature SpeA. Secretion of fusion prochymosin enzymatically and immunologically indistinguishable from bovine prochymosin was achieved after transformation of two stable protoplast type L-form strains derived from Proteus mirabilis. The secreted proenzyme was converted by autocatalytic processing to chymosin showing milk-clotting activity. In controlled laboratory fermentation processes, a maximum specific rate of activable prochymosin synthesis of 0.57 x 10(-3)/h was determined from the time courses of biomass dry weight and product formation. Yields as high as 40 +/- 10 micrograms/ml were obtained in the cell-free culture fluid of strain L99 carrying a naturally altered expression plasmid of increased segregational stability. The expression-secretion system described may be generally useful for production of recombinant mammalian proteins synthesized intracellularly as aberrantly folded insoluble aggregates. 相似文献
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Y. Molero C. Gumpert E. Serlachius P. Lichtenstein H. Walum D. Johansson H. Anckarsäter L. Westberg E. Eriksson L. Halldner 《Genes, Brain & Behavior》2013,12(3):305-310
The adenosine A2A receptor (ADORA2A) is linked to the dopamine neurotransmitter system and is also implicated in the regulation of alertness, suggesting a potential association with attention‐deficit hyperactivity disorder (ADHD) traits. Furthermore, animal studies suggest that the ADORA2A may influence ADHD‐like behavior. For that reason, the ADORA2A gene emerges as a promising candidate for studying the etiology of ADHD traits. The aim of this study was to examine the relationship between ADORA2A gene polymorphisms and ADHD traits in a large population‐based sample. This study was based on the Child and Adolescent Twin Study in Sweden (CATSS), and included 1747 twins. Attention‐deficit hyperactivity disorder traits were assessed through parental reports, and samples of DNA were collected. Associations between six single nucleotide polymorphisms (SNPs) and ADHD traits were examined, and results suggested a nominal association between ADHD traits and three of these SNPs: rs3761422, rs5751876 and rs35320474. For one of the SNPs, rs35320474, results remained significant after correction for multiple comparisons. These results indicate the possibility that the ADORA2A gene may be involved in ADHD traits. However, more studies replicating the present results are warranted before this association can be confirmed . 相似文献
4.
Impact of interpopulation divergence on additive and dominance variance in hybrid populations 总被引:2,自引:0,他引:2
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We present a theoretical proof that the ratio of the dominance vs. the additive variance decreases with increasing genetic divergence between two populations. While the dominance variance is the major component of the variance due to specific combining ability (sigma(SCA)(2)), the additive variance is the major component of the variance due to general combining ability (sigma(GCA)(2)). Therefore, we conclude that interpopulation improvement becomes more efficient with divergent than with genetically similar heterotic groups, because performance of superior hybrids can be predicted on the basis of general combining ability effects. 相似文献
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Eva Norén Selinus Yasmina Molero Paul Lichtenstein Tomas Larson Sebastian Lundstr?m Henrik Anckars?ter Clara Hellner Gumpert 《PloS one》2015,10(9)
Objective
Neurodevelopmental problems (NDPs) may influence the transition from childhood to adolescence. Our aim was to study long-term psychosocial outcomes of NDPs, focusing on ADHD.Method
Data was collected through a telephone interview with parents of twins at ages 9 or 12 years. NDP screen-positive children were clinically assessed at age 15; N = 450. Psychosocial outcome concerning peers, school, internalizing problems, antisocial behavior, alcohol misuse, drug misuse, and impaired daily functioning was examined.Results
Even after controlling for other NDP comorbidity, screen-positivity for ADHD doubled or tripled the odds of later psychosocial problems. When controlling for parental education level, the significant effect of ADHD remained only for antisocial behavior and impaired daily functioning.Conclusions
Signs of NDPs as well as other psychiatric diagnoses at ages 9 or 12 years are associated with a more problematic adolescence. However, despite the presence of comorbidity, early ADHD symptoms stand out as the most important risk factor for later antisocial development and impaired daily functioning. 相似文献7.
The outer-membrane protein ShlB of Serratia marcescens activates and secretes hemolytic ShlA into the culture medium. Without ShlB, inactive ShlA (termed ShlA*) remains in the
periplasm. Since Proteus mirabilis L-form cells lack an outer membrane and a periplasm, it was of interest to determine in which compartment recombinant ShlA*
and ShlB are localized and whether ShlB activates ShlA*. The cloned shlB and shlA genes were transcribed in P. mirabilis stable L-form cells by the temperature-inducible phage T7 RNA polymerase. Radiolabeling, Western blotting, and complementation
with C-terminally truncated ShlA (ShlA255) identified inactive ShlA* in the culture supernatant. ShlB remained cell-bound
and did not activate ShlA without integration in an outer membrane. Although hemolytic ShlA added to L-form cells had access
to the cytoplasmic membrane, it did not affect L-form cells. Synthesis of the large ShlA protein (165 kDa) in P. mirabilis L-form cells under phage T7 promoter control demonstrates that L-form cells are suitable for the synthesis and secretion
of large recombinant proteins. This property and the easy isolation of released proteins make L-form cells suitable for the
biotechnological production of proteins.
Received: 17 February 1998 / Accepted: 30 June 1998 相似文献
8.
Expression of the carboxypeptidase T gene from Thermoactinomyces vulgaris in stable protoplast type L-forms of Proteus mirabilis 总被引:1,自引:0,他引:1
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Growing L-form cells of Streptomyces hygroscopicus were shown to carry out 3-0-acylation and 14-C-hydroxylation of a macrolide glycoside suggesting that both types of bioconversion do neither require the intact cell wall nor the periplasmic space. 相似文献