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81.
82.
Summary Genomic clones encoding two Volvox -tubulin genes have been isolated and shown to represent the only two -tubulin genes in the genome. Restriction fragment length polymorphism analysis was used to demonstrate that the two genes are genetically linked. One of these genes was sequenced and the mRNA start site(s) determined by primer extension. A comparison of its sequence to those of the two -tubulin genes of Chlamydomonas revealed: (1) a high degree of conservation of the coding region, with the predicted amino acid sequence differing only in the C-terminal residue; (2) extensive sequence conservation in the 5 untranslated leader region and a 16 bp (putative regulatory) sequence in the promoter region; (3) the same number and location of introns, with a short region of homology in intron 1, but little significant homology in introns 2 and 3.  相似文献   
83.
Summary The structural genes (hup) of the H2 uptake hydrogenase of Rhodobacter capsulatus were isolated from a cosmid gene library of R. capsulatus DNA by hybridization with the structural genes of the H2 uptake hydrogenase of Bradyrhizobium japonicum. The R. capsulatus genes were localized on a 3.5 kb HindIII fragment. The fragment, cloned onto plasmid pAC76, restored hydrogenase activity and autotrophic growth of the R. capsulatus mutant JP91, deficient in hydrogenase activity (Hup-). The nucleotide sequence, determined by the dideoxy chain termination method, revealed the presence of two open reading frames. The gene encoding the large subunit of hydrogenase (hupL) was identified from the size of its protein product (68108 dalton) and by alignment with the NH2 amino acid protein sequence determined by Edman degradation. Upstream and separated from the large subunit by only three nucleotides was a gene encoding a 34 256 dalton polypeptide. Its amino acid sequence showed 80% identity with the small subunit of the hydrogenase of B. japonicum. The gene was identified as the structural gene of the small subunit of R. capsulatus hydrogenase (hupS). The R. capsulatus hydrogenase also showed homology, but to a lesser extent, with the hydrogenase of Desulfovibrio baculatus and D. gigas. In the R. capsulatus hydrogenase the Cys residues, (13 in the small subunit and 12 in the large subunit) were not arranged in the typical configuration found in [4Fe–4S] ferredoxins.  相似文献   
84.
Summary Beginning with a synthetic oligonucleotide probe derived from its amino acid sequence, we have identified, cloned and sequenced the hns gene encoding H-NS, an abundant Escherichia coli 15 kDa DNA-binding protein with a possible histone-like function. The amino acid sequence of the protein deduced from the nucleotide sequence is in full agreement with that determined for H-NS. By comparison of the restriction map of the cloned gene and of its neighboring regions with the physical map of E. coli K12 as well as by hybridization of the hns gene with restriction fragments derived from the total chromosome, we have located the hns gene oriented counterclockwise at 6.1 min on the E. coli chromosome, just before an IS30 insertion element.  相似文献   
85.
Summary The relationship between the promoter length of the Kluyveromyces fragilis -glucosidase gene and the level of its expression in Saccharomyces cerevisiae was studied by gene fusion between deleted promoter fragments of various lengths and the promoterless -galactosidase gene of Escherichia coli. The removal of a region from position-425 to-232 led to a tenfold increase in the expression of the gene. The same results were obtained for the reconstructed -glucosidase gene with the same promoter length. It is likely that the deletion of this part of the promoter removes negative regulatory elements which are functional in Saccharomyces cerevisiae. This increase in activity is the main event which may explain the high increase in gene expression (60-fold) previously observed for an upstream deletion obtained during subcloning experiments of the -glucosidase gene. It is also shown that the expression of the gene greatly depends upon the nature of the recipient strain, the growth phase of the cell and that of the vector carrying it.  相似文献   
86.
Summary The complete nucleotide sequence of the Escherichia coli cybB gene for diheme cytochrome b 561 and its flanking region was determined. The cybB gene comprises 525 nucleotides and encodes a 175 amino acid polypeptide with a molecular weight of 20160. From its deduced amino acid sequence, cytochrome b 561 is predicted to be very hydrophobic (polarity 33.7%) and to have three membrane spanning regions. Histidines, canonical ligand residues for protohemes, are localized in these regions, and the heme pockets are thought to be in the cytoplasmic membrane. No significant homology of the primary structure of cytochrome b 561 with those of other bacterial b-type cytochromes was observed.  相似文献   
87.
88.
Populations of viable sclerotia ofSclerotium rolfsii were highest in soil in a field in which tomato was planted for three successive years before sampling and in one in which tomato followed groundnut in the 2 years prior to this study. The lowest sclerotial numbers were recorded in fields in which groundnut followed maize or in which maize or sorghum was the last crop before sampling.  相似文献   
89.
90.
数种昆虫5S rRNA结构特点的比较   总被引:1,自引:0,他引:1  
比较已知结构的昆虫5S rRNA的核苷酸顺序,发现同科、同目的昆虫比不同科、不同目的昆虫有较少的核苷酸差别.根据Kimura和Ohta(1972)提出的经验公式,绘制了数种昆虫的系统发育图.结果表明,从分子进化得到的结论和经典分类基本上是一致的.根据DeWachter等(1982)提出的二级结构模型,归纳分析这些昆虫5S rRNA,发现保守位点与半保守位点(同一位点仅出现二种核苷酸残基)之和几乎占整个5S rRNA分子的100%.  相似文献   
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