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81.
Sequences encoding the protein and RNA components of ribonuclease P from Streptomyces bikiniensis var. zorbonensis. 总被引:4,自引:0,他引:4
The genes encoding the RNA (rnpB) and protein (rnpA) subunits of ribonuclease P (RNase P) of Streptomyces bikiniensis var. zorbonensis have been cloned by complementing the temperature-sensitive growth phenotype of Escherichia coli strains that carry mutations in these genes. The rnpB sequence of S. bikiniensis includes new covariations that lead to refinement of the previous secondary structure models for RNase P RNAs. The deduced amino acid sequence of S. bikiniensis RNase P is conserved with that of other known RNase P proteins only to a limited extent. Immediately upstream from rnpA is an open reading frame that codes for the highly conserved ribosomal protein, L34. This same gene arrangement occurs in all bacteria studied to date. 相似文献
82.
K Tory F Latif W Modi L Schmidt M H Wei H Li P Cobler M L Orcutt J Delisio L Geil 《Genomics》1992,13(2):275-286
We constructed a genetic map of 96 loci on the short arm of human chromosome 3 (3p) in 59 families provided by the Centre d'Etude du Polymorphisme Humaine (CEPH). Twenty-nine continuously linked loci were placed on the map with likelihood support of at least 1000:1; one locus, D3S213, was placed on the map with likelihood support of 871:1; D3Z1, an alpha satellite centromeric repeat probe, was placed on the map with likelihood support of 159:1; 65 loci were assigned regional locations. The average heterozygosity of the uniquely ordered markers was 49%. The map extends from 3p26, the terminal band of 3p, to the centromere (from D3S211 to D3Z1). Multipoint linkage analysis indicated that the male, female, and sex-averaged maps extend for 102, 147, and 116 cM, respectively. The mean genetic distance between uniquely ordered loci on the sex-averaged map was 4.0 cM. Probe density was greatest for the region of 3p between D3F15S2e and the telomere. The sex-averaged map contained two intervals greater than 10 cM. Seventeen probes were localized by fluorescence in situ hybridization. The loci described in this report will be useful in building an integrated genetic and physical map of this chromosome. 相似文献
83.
84.
R M Kessler M S Ansari D E Schmidt T de Paulis J A Clanton R Innis M al-Tikriti R G Manning D Gillespie 《Life sciences》1991,49(8):617-628
Epidepride, (S)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-5-iodo-2,3-dimethoxybenzamide+ ++, the iodine analogue of isoremoxipride (FLB 457), was found to be a very potent dopamine D2 receptor antagonist. Optimal in vitro binding required incubation at 25 degrees C for 4 h at pH 7.4 in a buffer containing 120 mM NaCl, 5 mM KCl, 2 mM CaCl2 and 1 mM MgCl2. Scatchard analysis of in vitro binding to striatal, medial frontal cortical, hippocampal and cerebellar membranes revealed a KD of 24 pM in all regions, with Bmax's of 36.7, 1.04, 0.85, and 0.37 pmol/g tissue, respectively. The Hill coefficients ranged from 0.91-1.00 in all four regions. The IC50's for inhibition of [125I]epidepride binding to striatal, medial frontal cortical, and hippocampal membranes for SCH 23390, SKF 83566, serotonin, ketanserin, mianserin, naloxone, QNB, prasozin, clonidine, alprenolol, and norepinephrine ranged from 1 microM to greater than 10 microM. Partial displacement of [125I]epidepride by nanomolar concentrations of clonidine was noted in the frontal cortex and hippocampus, but not in the striatum. Scatchard analysis of epidepride binding to alpha 2 noradrenergic receptors in the frontal cortex and hippocampus revealed an apparent KD of 9 nM. At an epidepride concentration equal to the KD for the D2 receptor, i.e. 25 pM, no striatal alpha 2 binding was seen and only 7% of the specific epidepride binding in the cortex or hippocampus was due to binding at the alpha 2 site. Correlation of inhibition of [3H]spiperone and [125I]epidepride binding to striatal membranes by a variety of D2 ligands revealed a correlation coefficient of 0.99, indicating that epidepride labels a D2 site. In vitro autoradiography revealed high densities of receptor binding in layers V and VI of prefrontal and cingulate cortices as well as in striatum. In vivo rat brain uptake revealed a hippocampal:cerebellar and frontal cortical:cerebellar ratio of 2.2:1 which fell to 1.1:1 following haloperidol pretreatment. These properties suggest that [125I]epidepride is a superior radioligand for the in vitro and in vivo study of striatal and extrastriatal dopamine D2 receptors. 相似文献
85.
E. J. Nücken R. B. Henschke F. R. J. Schmidt 《Molecular & general genetics : MGG》1991,229(1):137-146
Summary Tn21-related transposons are widespread among bacteria and carry various resistance determinants at preferential sites, hs1 and hs2. In an in vivo integrative recombination assay it was demonstrated that these hot spots direct the integration of aminoglycoside resistance genes like aadB from Klebsiella pneumoniae and aacAI from Serratia marcescens, in a recA
– background. The maximum required recognition sequence which must be present in both the donor and recipient plasmids is 5 CTAAAACAAAGTTA 3 (hs2). The double-site-specific recombination occurred with a frequency of 10–5–10–6. The resulting structures include not only replicon fusion products but also more complex structures carrying two copies of the donor plasmid or simply the donor gene flanked by hs elements. hs1 and hs2 are thought to act as recognition sites for a trans-acting site-specific recombinase. By the use of Tn21 deletion derivatives, it has been shown that the recombinase is not encoded by Tn21. This new integrative recombination system is involved in the acquisition of new genes by Tn21-related transposons and their spread among bacterial populations. 相似文献
86.
H Bahl G Burchhardt A Spreinat K Haeckel A Wienecke B Schmidt G Antranikian 《Applied and environmental microbiology》1991,57(5):1554-1559
The nucleotide sequence of the alpha-amylase gene (amyA) from Clostridium thermosulfurogenes EM1 cloned in Escherichia coli was determined. The reading frame of the gene consisted of 2,121 bp. Comparison of the DNA sequence data with the amino acid sequence of the N terminus of the purified secreted protein of C. thermosulfurogenes EM1 suggested that the alpha-amylase is translated from mRNA as a secretory precursor with a signal peptide of 27 amino acid residues. The deduced amino acid sequence of the mature alpha-amylase contained 679 residues, resulting in a protein with a molecular mass of 75,112 Da. In E. coli the enzyme was transported to the periplasmic space and the signal peptide was cleaved at exactly the same site between two alanine residues. Comparison of the amino acid sequence of the C. thermosulfurogenes EM1 alpha-amylase with those from other bacterial and eucaryotic alpha-amylases showed several homologous regions, probably in the enzymatically functioning regions. The tentative Ca(2+)-binding site (consensus region I) of this Ca(2+)-independent enzyme showed only limited homology. The deduced amino acid sequence of a second obviously truncated open reading frame showed significant homology to the malG gene product of E. coli. Comparison of the alpha-amylase gene region of C. thermosulfurogenes EM1 (DSM3896) with the beta-amylase gene region of C. thermosulfurogenes (ATCC 33743) indicated that both genes have been exchanged with each other at identical sites in the chromosomes of these strains. 相似文献
87.
J A Widness S T Sawyer R L Schmidt D H Chestnut 《Journal of developmental physiology》1991,15(3):139-143
We administered tracer quantities of biologically active 125I-labelled recombinant human erythropoietin by intravenous bolus injection to seven late gestation pregnant ewes. Maternal and fetal blood was sampled over the subsequent six hours and assayed for erythropoietin-specific radioactivity. Despite the expected increase in maternal plasma immunoprecipitable 125I-labelled erythropoietin radioactivity, fetal plasma levels remained unchanged throughout the study. In addition, erythropoietin receptors were not detected in ovine and human placental tissue. We conclude that biologically active 125I-labelled erythropoietin does not cross the placenta from mother to fetus in measurable quantities in sheep, and likely in humans. Thus, these data indicate the levels of erythropoietin measured in fetal plasma are reflective of fetal, and not maternal, erythropoietin production and elimination. 相似文献
88.
89.
Mammalian sex chromosomes evolved (and are still evolving) from a homomorphic pair by the progressive loss of active genes from the Y chromosome. Among the changes that have accompanied this differentiation, it is difficult to determine causes, effects and correlates. Comparative studies suggest that the choice of a gene, and thus a chromosome pair, to control the sex-determining pathway may be quite arbitrary, and that sex chromosomes and sex-determining genes are more likely to be the products of random changes than the products of selection for function. 相似文献
90.
Ralf Schmidt Klaus Neubert Alfred Barth Claus Liebmann Martin Schnittler Nga N. Chung Peter W. Schiller 《Peptides》1991,12(6):1175-1180
Cyclic analogues of the β-casein-derived opioid peptide β-casomorphin-5 (H-Tyr-Pro-Phe-Pro-Gly-OH) were prepared through substitution of the Pro2 residue with various ,ω-diamino acid residues (lysine, ornithine, 2,4-diaminobutyric acid) and cyclization of the ω-amino group to the C-terminal carboxyl function. Compounds of this type, with D-configuration at the 2-position residue, showed high opioid receptor affinity with some preference for μ receptors over δ receptors, high potency in the guinea pig ileum assay and considerable activity in the mouse vas deferens assay. Configurational inversion at the 4-position in these cyclic analogues resulted in enhanced affinity for both μ and δ receptors, whereas N-methylation of the Phe3 residue produced a potency decrease. 相似文献