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排序方式: 共有73条查询结果,搜索用时 15 毫秒
31.
32.
U Englisch S Englisch P Markmeyer J Schischkoff H Sternbach H Kratzin F Cramer 《Biological chemistry Hoppe-Seyler》1987,368(8):971-979
The ILS1 gene encoding for cytoplasmic isoleucyl-tRNA synthetase from Saccharomyces cerevisiae was subcloned from a 5.4-kb insert of the shuttle vector YEp13 to M13mp8 and M13mp9. Nucleotide sequence analysis of a 4.3-kb BamHI-HpaI fragment revealed a single open reading frame from which we deduced the amino-acid sequence of the enzyme. Independently obtained amino-acid sequence information from ten tryptic peptides of the purified enzyme confirmed the gene-derived structure. The enzyme is comprised of 1073 amino-acids consistent with earlier determinations of its molecular mass. The codon usage of ILS1 is typical of abundant yeast proteins. A significant homology to E. coli isoleucyl- and valyl-tRNA synthetases as well as to yeast valyl-tRNA synthetase was detected. The characteristic amino-acid residues of the aminoacyl-adenylate site and of the potential binding site of the 3'-end of tRNA found in other synthetases are present in the structure. 相似文献
33.
A GFP-MAP4 reporter gene for visualizing cortical microtubule rearrangements in living epidermal cells 总被引:15,自引:7,他引:8
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J Marc CL Granger J Brincat DD Fisher Th Kao AG McCubbin RJ Cyr 《The Plant cell》1998,10(11):1927-1940
Microtubules influence morphogenesis by forming distinct geometrical arrays in the cell cortex, which in turn affect the deposition of cellulose microfibrils. Although many chemical and physical factors affect microtubule orientation, it is unclear how cortical microtubules in elongating cells maintain their ordered transverse arrays and how they reorganize into new geometries. To visualize these reorientations in living cells, we constructed a microtubule reporter gene by fusing the microtubule binding domain of the mammalian microtubule-associated protein 4 (MAP4) gene with the green fluorescent protein (GFP) gene, and transient expression of the recombinant protein in epidermal cells of fava bean was induced. The reporter protein decorates microtubules in vivo and binds to microtubules in vitro. Confocal microscopy and time-course analysis of labeled cortical arrays along the outer epidermal wall revealed the lengthening, shortening, and movement of microtubules; localized microtubule reorientations; and global microtubule reorganizations. The global microtubule orientation in some cells fluctuates about the transverse axis and may be a result of a cyclic self-correcting mechanism to maintain a net transverse orientation during cellular elongation. 相似文献
34.
The restriction enzyme TaqI digests 0.2% of the genomic DNA from the
grasshopper Caledia captiva to a family of sequences 168 bp in length
(length of consensus sequence). The sequence variation of this "Taq family"
of repeat units was examined among four races from C. captiva to assay the
pattern of evolution within this highly repeated DNA. The Taq-family
repeats are located in C-banded heterochromatin on at least one member of
each homologous pair of chromosomes; the locations range from centromeric
to telomeric. Thirty-nine cloned repeats isolated from two population 1A
individuals along with 11 clones from seven populations taken from three of
the races demonstrated sequence variation at 72 positions. Pairwise
comparisons of the cloned repeats, both within an individual and between
different races, indicate that levels of intraspecific divergence, as
measured by reproductive incompatibility, do not correlate with sequence
divergence among the 168-bp repeats. A number of subsequences within the
repeat remain unchanged among all 50 clones; the longest of these is 18 bp.
That the same 18-bp subsequence is present in all clones examined is a
finding that departs significantly (P less than 0.01) from what would be
expected to occur at random. Two other cloned repeats, from a
reproductively isolated race of C. captiva, have sequences that show 56%
identity with this 18-bp conserved region. An analysis showed that the
frequency of occurrence of an RsaI recognition site within the 168- bp
repeat in the entire Taq family agreed with that found in the cloned
sequences. These data, along with a partial sequence for the entire Taq
family obtained by sequencing uncloned repeats, suggest that the consensus
sequence from the cloned copies is representative of this highly repeated
family and is not a biased sample resulting from the cloning procedure. The
18-bp conserved sequence is part of a 42-bp sequence that possesses dyad
symmetry typical of protein-binding sites. We speculate that this may be
significant in the evolution of the Taq family of sequences.
相似文献
35.
Codon-anticodon interaction at the ribosomal E site 总被引:3,自引:0,他引:3
H J Rheinberger H Sternbach K H Nierhaus 《The Journal of biological chemistry》1986,261(20):9140-9143
The question of whether or not the tRNA at the third ribosomal binding site specific for deacylated tRNA (E site) undergoes codon-anticodon interaction was analyzed as follows. Poly(U)-programmed ribosomes each carrying two [14C]tRNAPhe molecules were subjected to a chasing experiment using various tRNA species. At 0 degree C Ac[3H]Phe-tRNAPhe did not trigger any chasing whereas deacylated cognate tRNAPhe provoked a strong effect; non-cognate tRNALys was totally ineffective. This indicates that the second [14C]tRNAPhe cannot be present at the A site but rather at the E site (confirming previous observations). In the presence of poly(U) or poly(A) ribosomes bound the cognate tRNA practically exclusively as second deacylated tRNA, i.e. [14C]tRNAPhe and [14C]tRNALys, respectively. Thus, the second deacylated tRNA binds in a codon-dependent manner. [14C]tRNALys at the P site and Ac[3H]Lys-tRNALys at the A site of poly(A)-primed ribosomes were translocated to the E and P sites, respectively, by means of elongation factor G. The E site-bound [14C]tRNALys could be significantly chased by cognate tRNALys but not by non-cognate tRNAPhe, indicating the coded nature of the E site binding. Additional evidence is presented that the ribosome accommodates two adjacent codon-anticodon interactions at either A and P or P and E sites. 相似文献
36.
37.
Discrimination factors (D) which are characteristic for discrimination between lysine and 19 naturally occurring non-cognate amino acids have been determined from kcat and Km values for native and phosphorylated lysyl-tRNA synthetases from yeast. Generally, both species of this class II aminoacyl-tRNA synthetase are considerably less specific than the class I synthetases specific for isoleucine, valine, tyrosine, and arginine. D values of the native enzyme are in the range 90-1700, D values of the phosphorylated species in the range 40-770. The phosphorylated enzyme acts faster and less accurately. In aminoacylation of tRNALys-C-C-A(2'NH2) discrimination factors D1 vary over 30-980 for the native and over 8-300 for the phosphorylated enzyme. From AMP formation stoichiometry and D1 values pretransfer proof-reading factors (II1) of 1.1-56 were calculated for for the native enzyme, factors of 1.0-44 for the phosphorylated species. Post-transfer proof-reading factors (II2) were calculated from D values and AMP formation stoichiometry in acylation of tRNALys-C-C-A. Pretransfer proof-reading is the main correction step, posttransfer proof-reading is less effective or negligible (II2 approximately 1-8). Initial discrimination factors (I), which are due to differences in Gibbs free energies of binding between lysine and noncognate substrates (delta delta GI), were calculated from discrimination and proof-reading factors. In contrast to class I synthetases, for lysyl-tRNA synthetase only one initial discrimination step can be assumed and amino acid recognition is reduced to a three-step process instead of the four-step recognition observed for the class I synthetases. Plots of delta delta GI values against accessible surface areas of amino acids show clearly that phosphorylation of the enzyme changes the structures of the amino acid binding sites. This is illustrated by a hypothetical 'stopper model' of these sites. 相似文献
38.
Evans KA Shearer BG Wisnoski DD Shi D Sparks SM Sternbach DD Winegar DA Billin AN Britt C Way JM Epperly AH Leesnitzer LM Merrihew RV Xu RX Lambert MH Jin J 《Bioorganic & medicinal chemistry letters》2011,21(8):2345-2350
A series of phenoxyacetic acids as subtype selective and potent hPPARδ partial agonists is described. Many analogues were readily accessible via a single solution-phase synthetic route which resulted in the rapid identification of key structure-activity relationships (SAR), and the discovery of two potent exemplars which were further evaluated in vivo. Details of the SAR, optimization, and in vivo efficacy of this series are presented herein. 相似文献
39.
BACKGROUND: Insect symbionts employ multiple strategies to enhance their spread through populations, and some play a dual role as both a mutualist and a reproductive manipulator. It has recently been found that this is the case for some strains of Wolbachia, which both cause cytoplasmic incompatibility and protect their hosts against viruses. Here, we carry out the first test as to whether a male-killing strain of Wolbachia also provides a direct benefit to its host by providing antiviral protection to its host Drosophila bifasciata. We infected flies with two positive sense RNA viruses known to replicate in a range of Drosophila species (Drosophila C virus and Flock House virus) and measure the rate of death in Wolbachia positive and negative host lines with the same genetic background. RESULTS: Both viruses caused considerable mortality to D. bifasciata flies, with Drosophila C virus killing 43% more flies than the uninfected controls and Flock House virus killing 78% more flies than the uninfected controls. However, viral induced mortality was unaffected by the presence of Wolbachia. CONCLUSION: In the first male-killing Wolbachia strain tested for antiviral effects, we found no evidence that it conferred protection against two RNA viruses. We show that although antiviral resistance is widespread across the Wolbachia phylogeny, the trait seems to have been lost or gained along some lineages. We discuss the potential mechanisms of this, and can seemingly discount protection against these viruses as a reason why this symbiont has spread through Drosophila populations. 相似文献
40.