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51.
52.
Nucleotide sequence and expression of cheF, an essential gene for chemotaxis in Bacillus subtilis. 总被引:4,自引:4,他引:0
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The cheF gene, which is involved in chemotaxis in Bacillus subtilis, has been cloned, expressed, and sequenced. This gene is contained in a 0.7-kilobase PstI DNA fragment that was isolated from a lambda Charon 4A B. subtilis chromosomal DNA library. This fragment was subcloned into the expression vector pSI-1 and shown to complement the cheF mutation both for chemotaxis and for methanol production in response to the addition of attractants. Plasmid-encoded DNA expression in B. subtilis maxicells indicated that a membrane-associated polypeptide of 20-kilodaltons was expressed from this 0.7-kilobase DNA. The nucleotide sequence of this DNA fragment was determined, and an open reading frame capable of encoding a putative 175-amino-acid protein (Mr 20,002) was identified. In an effort to understand the function of the cheF protein, the dosage of the cheF gene product was varied by altering the concentration of IPTG (isopropyl-beta-D-thiogalactopyranoside) during growth. In the presence of high concentrations of IPTG, chemotaxis was inhibited and methanol production was impaired. 相似文献
53.
Summary Better production of pro-urokinase from human cell line was observed with 5% serum containing medium than 10% or serum free medium on Cytodex II under perfusion chemostat operations, showing 0.8×10–5 (IU/daycell) of maximum productivity at 0.020 (l/h) of dilution rate in 5% serum medium, which corresponds to 800 IU/mL at this dilution rate. Conversion of pro-urokinase was reduced in the serum-containing media. 相似文献
54.
本文研究了不同底物(N_2,H_2,N_2O,NaN_3,C_2H_2)对棕色固氮菌固氮酶及其钼铁蛋白荧光光谱的影响。结果表明,上述底物均能络合在钼铁蛋白及固氮酶上,但络合程度不同,从而为固氮酶系统有多个不同的底物络合中心,底物络合中心在钼铁蛋白分子上,铁蛋白对钼铁蛋白有变构作用,提供了光谱学证据。 相似文献
55.
We report the isolation and characterization of two new genomic loci corresponding to the mouse Dishevelled (Dvl) genes Dvl2 and Dvl3. The Dvl genes are homologs of the Drosophila dsh segment polarity gene, and are involved in the Wnt/wingless signal transduction pathway. Dvl2 and Dvl3 genomic clones were isolated from a mouse 129 strain λFIXII genomic library and have identical exon/intron organization to Dvll. All three Dishevelled genes span 15 exons and 14 introns and have a number of conserved splice junction sites. 相似文献
56.
槐种子发育中胚乳细胞半乳甘露聚糖积累的研究 总被引:2,自引:0,他引:2
槐 ( Sophora japonica L.)开花约 60 d至种子成熟 ,为胚乳半乳甘露聚糖积累期。用组织化学方法 ,对储藏于胚乳细胞壁上的半乳甘露聚糖的形成积累进行了观察 ,结果表明 ,半乳甘露聚糖最先在邻近胚的胚乳细胞的粗面内质网的囊泡腔内形成 ,并通过细胞质膜分泌至细胞壁周围。此后 ,半乳甘露聚糖的积累逐渐向种皮方向扩展 ,及至种子成熟时 ,除糊粉层外 ,所有胚乳细胞几乎全由多糖所填充。此外 ,对半乳甘露聚糖发生部位及其积累过程的消长变化进行了讨论 相似文献
57.
A. Petronis A. S. Bassett W. G. Honer J. B. Vincent Y. Tatuch T. Sasaki D. J. Ying T. A. Klempan J. L. Kennedy 《American journal of human genetics》1996,59(4):905-911
Evidence for genetic anticipation has recently become an important subject of research in clinical psychiatric genetics. Renewed interest in anticipation was evoked by molecular genetic findings of a novel type of mutation termed "unstable DNA." The unstable DNA model can be construed as the "best fit" for schizophrenia twin and family epidemiological data. We have performed a large-scale Southern blot hybridization, asymmetrical PCR-based, and repeat expansion-detection screening for (CAG)n/(CTG)n and (CCG)n/(CGG)n expansions in eastern Canadian schizophrenia multiplex families demonstrating genetic anticipation. There were no differences in (CAG)n/(CTG)n and (CCG)n/(CGG)n pattern distribution either between affected and unaffected individuals or across generations. Our findings do not support the hypothesis that large (CAG)n/(CTG)n or (CCG)n/(CGG)n expansions are the major etiologic factor in schizophrenia. A separate set of experiments directed to the analysis of small (30-130 trinucleotides), Huntington disease-type expansions in individual genes is required in order to fully exclude the presence of (CAG)n/(CTG)n- or (CCG)n/(CGG)n-type unstable mutation. 相似文献
58.
Kjetil Taskn Rigmor Solberg Ying Zhao Vidar Hansson Tore Jahnsen Michael J. Siciliano 《Genomics》1996,36(3):535
We have determined the chromosomal localization of the gene for the catalytic subunit Cα of cAMP-dependent protein kinase (locus PRKACA) to human chromosome 19 using polymerase chain reaction (PCR) and Southern blot analysis of two different somatic cell hybrid mapping panels. In addition, PCR analysis of a chromosome 19 mapping panel revealed the presence of a human Cα-specific amplification product only in cell lines containing the region 19p13.1 to 19q12. Finally, two-color fluorescencein situhybridization to metaphase chromosomes using the human Cα cDNA and human chromosome 19 inter-Alu-PCR product as probes localized the human Cα gene to chromosome region 19p13.1. 相似文献
59.
Yeehn Yeeh Soon Suk Kang Hye Gi Chung Mun Su Chung Myong Gi Chung 《Journal of plant research》1996,109(2):161-168
Vitex rotundifolia L.f. is a woody perennial and has sexual and asexual modes of reproduction. Allozyme study was conducted on 550 plants in
13 Korean populations. The levels of genetic variability and divergence within and among populations, respectively, are considerably
lower and higher than the mean values for woody plants with similar life history tralts. Mean percentage of polymorphic loci
(P
P), mean number of alleles per locus (A
P), and mean genetic diversity (He
P) within populations ofV. rotundifolia were: 16.7%, 1.21, and 0.047. On average, about 79% of the total variation inV. rotundifolia was common to all populations (meanG
ST=0.208). In addition, significant differences in allele frequencies among populations were found in all polymorphic loci examined
(P<0.001). On the other hand, levels of genotypic diversity within and among populations were moderate. About 44% (18/41) of
multilocus genotypes were “local genotypes” (genotypes occurring in only one population), whereas only one “widespread genotype”
(genotypes occurring in more than 75% of the populations) were detected. The mean number of multilocus genotypes per population
(G) and mean genotypic diversity index (D
G) were 8.4 and 0.74, respectively. Most common multilocus genotypes found in populations were homozygous for five polymorphic
loci. The abundance of ramets of these genets is responsible for the low levels of expected heterozygosity within populations.
The results indicate that clonal reproduction may act as an enhancer of genetic drift by reducing effective size of local
populations ofV. rotundifolia. 相似文献
60.
In the present study we have characterized the synthesis of members of the HSP30 family during Xenopus laevis development using a polyclonal antipeptide antibody derived from the carboxyl end of HSP30C. Two-dimensional PAGE/immunoblot analysis was unable to detect any heat-inducible small HSPs in cleavage, blastula, gastrula, or neurula stage embryos. However, heat-inducible accumulation of a single protein was first detectable in early tailbud embryos with an additional 5 HSPs at the late tailbud stage and a total of 13 small HSPs at the early tadpole stage. In the Xenopus A6 kidney epithelial cell line, a total of eight heat-inducible small HSPs were detected by this antibody. Comparison of the pattern of protein synthesis in embryos and somatic cells revealed a number of common and unique heat inducible proteins in Xenopus embryos and cultured kidney epithelial cells. To specifically identify the protein product of the HSP30C gene, we made a chimeric gene construct with the Xenopus HSP30C coding sequence under the control of a constitutive promoter. This construct was microinjected into fertilized eggs and resulted in the premature and constitutive synthesis of the HSP30C protein in gastrula stage embryos. Through a series of mixing experiments, we were able to specifically identify the protein encoded by the HSP30C gene in embryos and somatic cells and to conclude that HSP30C synthesis was first heat-inducible at the early tailbud stage of development. The differential pattern of heat-inducible accumulation of members of the HSP30 family during Xenopus development suggests that these proteins may have distinct functions at specific embryonic stages during a stress response. 相似文献