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Kirromycin-resistant mutant forms of elongation factor Tu, which are coded by tufA (Ar) or tufB (Bo) and are associated with an increased rate of translational error formation, have been analysed. In vivo, Ar was found to increase misreading as well as suppression of non-sense codons irrespective of Bo in a strain with wild type ribosomes. It is therefore not necessary to evoke both tufA (Ar) and tufB (Bo) mutations together in order to increase translational error as suggested earlier [1]. When combined with a hyperaccurate ribosomal rpsL (S12) mutation, Ar counteracts the restrictive effects on translational error formation caused by the altered protein S12, thus restoring the levels of missense error in vitro and non-sense error and suppression in vivo to near wild type values. As judged from in vitro experiments this results principally from a lowered selectivity of the Ar ternary complex at the initial discrimination step on the ribosome during translation. In vivo, this compensatory effect on the rpsL mutation on non-sense error formation and suppression is seen irrespective of the nature of tRNA or codon context. Furthermore, the tufA mutation enhances the cellular growth rate of the rpsL mutant, whereas it decreases growth of strains with normal ribosomes. Inactivation of one of the two genes coding for EF-Tu (tufB), while leaving the other gene (tufA) intact, can by itself, increase non-sense error formation and suppression. 相似文献
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Herman Adlercreutz Yaghoob Mousavi Jim Clark Krister Hckerstedt Esa Hmlinen Kristiina Whl Taru Mkel Tapio Hase 《The Journal of steroid biochemistry and molecular biology》1992,41(3-8)
Thirty postmenopausal women (11 omnivores, 10 vegetarians and 9 apparently healthy women with surgically removed breast cancer) were investigated with regard to the association of their urinary excretion of estrogens, lignans and isoflavonoids (all diphenols) with plasma sex hormone binding globulin (SHBG). A statistically significant positive correlation between urinary total diphenol excretion and plasma SHBG was found which remained statistically significant after elimination of the confounding effect of body mass determined by body mass index (BMI). Furthermore we found a statistically significant negative correlation between plasma SHBG and urinary excretion of 16α-hydroxyestrone and estriol which also remained significant after eliminating the effect of BMI. Furthermore we observed that enterolactone (Enl) stimulates the synthesis of SHBG by HepG2 liver cancer cells in culture acting synergistically with estradiol and at physiological concentrations. Enl was rapidly conjugated by the liver cells, mainly to its monosulfate. Several lignans and the isoflavonoids daidzein and equol were found to compete with estradiol for binding to the rat uterine type II estrogen binding site (the s.c. bioflavonoid receptor). It is suggested that lignans and isoflavonoids may affect uptake and metabolism of sex hormones by participating in the regulation of plasma SHBG levels and in this way influence their biological activity and that they may inhibit cancer cell growth like some flavonoids by competing with estradiol for the type II estrogen binding sites. 相似文献
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The ceIV1 gene encoding a secreted cellulase (CelV1) of Erwinia carotovora subsp. carotovora SCC3193 was cloned and its nucleotide sequence determined. The gene contains an open reading frame of 1511 by and codes for an exported protein of 504 amino acids. The predicted amino acid sequence of Ce1V1 was highly similar to that of CeIV of another E. c. subsp. carotovora strain SCRI193 but completely different from the previously characterized cellulase, CelS, of the strain SCC3193. Gene fusions to the lacZ reporter were employed to characterize the regulation of celV1 and celS. Both genes are coordinately induced in a growth phase-dependent manner and are catabolite repressed. Expression of celV1 but not celS was stimulated by plant extracts. The celS gene was expressed at a much lower level than celV1 under all conditions tested. Inactivation of the celV1 gene in E. c. subsp. carotovora strain SCC3193 by marker exchange showed that celV1 encodes the major cellulase of strain SCC3193, as the resulting mutant strain SCC6001 was devoid of cellulase activity. Ce1Vl mutants exhibited reduced virulence suggesting that CelV1, although not absolutely required for pathogenicity, enhances the ability of strain SCC3193 to macerate plant tissue. Inactivation of the celS gene in the celV1 mutant did not lead to any further decrease in virulence. 相似文献
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Salicylic acid and the plant pathogen Erwinia carotovora induce defense genes via antagonistic pathways 总被引:3,自引:2,他引:1
Sabina Vidal Inés Ponce de León Jürgen Denecke E. Tapio Palva 《The Plant journal : for cell and molecular biology》1997,11(1):115-123
Infection of tobacco plants with the plant pathogenic bacterium Erwinia carotovora subsp. carotovora or treatment of plants with Erwinia -derived elicitor preparations leads to the induction of a number of genes thought to play a role in plant defense response to pathogens. In order to determine the role of salicylic acid (SA) in the induction of the Erwinia responsive genes, the accumulation of mRNAs for these and other genes encoding pathogenesis-related proteins (PR genes) in response to both Erwinia elicitors and SA was determined. PR genes were identified which were preferentially induced by Erwinia elicitor preparations, one gene was induced by SA but not by Erwinia , and another gene was induced by both type of treatments. The differential expression of these genes and the timing of induction suggest that SA is not the signal molecule leading to the early response of plants to Erwinia . This was demonstrated by experiments using transgenic NahG plants that overproduce a salicylate hydroxylase inactivating SA. The elicitation of PR genes by Erwinia was similar in NahG and wild-type plants. Therefore, induction of plant defense genes by Erwinia and SA seems to be by two distinct pathways leading to expression of separate sets of genes. Furthermore, we could demonstrate that Erwinia elicitors antagonize the SA-mediated induction of PR genes. Similarly, SA appeared to inhibit the induction of PR genes elicited by Erwinia . The observed antagonism between the two signal transduction pathways indicates the presence of a common regulatory element in both pathways that acts downstream of SA in the SA-mediated response. 相似文献
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Maternal origin of nucleated erythrocytes in peripheral venous blood of pregnant women 总被引:3,自引:0,他引:3
Anna Slunga-Tallberg Wa'el El-Rifai Mauri Keinänen Kari Ylinen Tapio Kurki Katherine Klinger Olavi Ylikorkala Sakari Knuutila 《Human genetics》1995,96(1):53-57
We studied the origin of nucleated red blood cells (NRBC) in peripheral venous blood samples from 40 pregnant women carrying a male fetus, using a technique that allows direct chromosomal analysis by in situ hybridisation on immunologically and morphologically classified cells. Samples from ten nulligravid women were studied as controls. NRBC were enriched by negative magnetic activated cell sorting (miniMACS) using anti-CD45 monoclonal antibody. NRBC were detected by alkaline phosphatase anti-alkaline phosphatase immunostaining using a monoclonal anti-glycophorin A antibody. The origin of the NRBC was determined by fluorescence in situ hybridisation using X and Y specific probes. NRBC were found in 37 of the 40 pregnant women at a range of 1 to 230 per 20 ml of venous blood and in 6 of the 10 controls at a range of 1 to 3 per 20 ml of venous blood. All NRBC detected in the pregnant women were evidently of maternal origin, and in the pregnant women the number of NRBC was significantly higher (P < 0.05) than in the controls. Pregnancy per se seems to induce the appearance of maternal NRBC in the circulation, and it cannot therefore be assumed that NRBC isolated from the maternal blood are of fetal origin on the basis of morphology alone. Discrimination of fetal NRBC must occur for prenatal diagnosis of fetal genetic disorders. 相似文献
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Ashis K. Sen Kalyan K. Sarkar Pronobesh C. Mazumder Nilima Banerji Raimo Uusvuori Tapio A. Hase 《Phytochemistry》1982,21(7):1747-1750
Three new tetraoxygenated xanthones (garcinones A, B and C), each disubstituted with C5-units, have been isolated from the chloroform extract of the fruit-hulls of Garcinia mangostana. Their structures were established by a combination of spectral interpretation and chemical correlation. 相似文献
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Transposon-insertion mutants of Escherichia coli K12 defective in a component common to galactose and ribose chemotaxis. 总被引:9,自引:0,他引:9
Shigeaki Harayama E. Tapio Palva Gerald L. Hazelbauer 《Molecular & general genetics : MGG》1979,171(2):193-203
Summary From a collection of 8,000 transposon-insertion mutants of Escherichia coli K12 we identified two mutations, trg-1::Tn5 and trg-2::Tn10, that simultaneously eliminate chemotactic response to ribose and galactose, two attractants recognized by independent receptors. We show that these transposon-insertions confer a Trg phenotype, indicating that this specific pattern of tactic defects is a null phenotype. The two mutation sites are cotransductionally linked to an extend consistent with placement in the same gene. The Trg phenotype of a family of deletion mutants produced by curing trg-2::Tn10 implies that trg is a single gene. Experiments with appropriate F-primes and Hfr's locate the trg locus at approximately 31 min on the linkage map, with a marker order: pyrF-rac-(P.O. 43)-trg-man.We also found one trg mutant whose Trg phenotype was not linked to a transposon-insertion but is probably the result of a mutator activity in the parent strain. Selection of transposon-insertions near, but not in trg allowed demonstration of a very close linkage between the spontaneous trg-3 and the transposon-generated trg's, indicating all three mutations are probably in the same gene. In our manipulations of transposon-insertions we found that Tn5 had a tendency to translocate from its initial site of insertion while Tn10 was relatively stable.The trg-product is probably a chemotactic signal transducer, which interacts directly with two independent receptor proteins and transmits information to the central chemotactic machinery. 相似文献