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1.
2.
Identification of an amber nonsense mutation in the rosy516 gene by germline transformation of an amber suppressor tRNA gene. 总被引:7,自引:0,他引:7 下载免费PDF全文
Seven xanthine dehydrogenase and cross-reacting material negative Drosophila melanogaster rosy stocks were screened for amber and ochre nonsense mutations. Amber and ochre nonsense suppressors were created by site-directed mutagenesis starting from a wild-type tRNA(Tyr) gene. The suppressor tRNA genes were subcloned into a pUChsneo transformation vector providing heat-shock controlled neomycin resistance. The seven rosy stocks were germline transformed with amber and ochre tDNA(Tyr), and the G1 generation was screened for Geneticin resistance. Surviving rosy516 flies transformed with the amber suppressor showed an eye colour intermediate between the original ry516 stock and the wild-type, suggesting that ry516 is an amber nonsense mutant. This was confirmed by sequencing the relevant part of the ry516 gene; the analysis revealed a C-to-T transition in a CAG glutamine codon at nucleotide 1522 of the wild-type rosy gene. 相似文献
3.
The amino-acid sequence from the bilin binding protein (BBP) of the butterfly Pieris brassicae has been determined. The apoprotein with a length of 173 amino-acid residues has a molecular mass of 19,676 Da. The sequence analysis was performed by automated Edman degradation of the intact apoprotein and of fragments as large as possible generated from different digestions. The 3-dimensional structure of BBP, determined by Huber et al. (Huber, R., Schneider, M., Epp, O., Mayr, I., Messerschmidt, A., Pflugrath, J. & Kayser, H. (1987) J. Mol. Biol. 195, 423-434 and Huber, R., Schneider, M., Mayr, I., Müller, R., Deutzmann, R., Suter, F., Zuber, H., Falk, H. & Kayser, H. (1987) J. Mol. Biol. 198, 499-513) down to 2-A resolution, exhibits a similar conformation to the human retinol binding protein. Sawyer (Sawyer, L. (1987) Nature (London) 327, 659) demonstrated that proteins from a wide variety of sources can be gathered into a "superfamily". Computer searches of data banks yielded in a new member of this superfamily, namely human alpha 1-acid glycoprotein. One of the functions of the listed proteins is to bind and transport small hydrophobic molecules in serum. 相似文献
4.
Queuosine modification of the wobble base in tRNAHis influences ''in vivo'' decoding properties. 总被引:5,自引:1,他引:4 下载免费PDF全文
The 'in vivo' decoding properties of four tRNAHis isoacceptors, two from Drosophila melanogaster and two from brewer's yeast, were studied after their microinjection, along with turnip yellow mosaic virus (TYMV) coat protein mRNA, into Xenopus laevis oocytes. The two Drosophila isoacceptors are identical besides containing either a guanosine (G) or the hypermodified nucleoside queuosine (Q) in the wobble position. The brewer's yeast isoacceptors differ by four bases in the anticodon stem, and by one base in the amino acceptor stem. Our results show that, under competing 'in vivo' conditions, the Drosophila tRNAHis with the anticodon GUG clearly prefers the histidine codon CAC to the codon CAU, whereas little preference is observed for the tRNAHis with the anticodon QUG for the codon CAU, and no preference for either codon by the two yeast isoacceptors. Hence, it can be concluded that the presence of the Q-base clearly affects the choice of the codon. This is the first demonstration of an 'in vivo' codon preference by tRNA isoacceptors differing in the modification of the wobble base during the elongation step of protein synthesis. These results imply that one function of the Q-base is at the translational level. 相似文献
5.
The primary structure of Bacillus cereus neutral proteinase and comparison with thermolysin and Bacillus subtilis neutral proteinase 总被引:11,自引:0,他引:11
The complete amino-acid sequence of a neutral proteinase, produced by Bacillus cereus, was determined by protein sequencing. The neutral proteinase consists of 317 amino-acid residues. The primary structure is 70% homologous to thermolysin, a thermostable neutral proteinase and 45% homologous to Bacillus subtilis neutral proteinase. The zinc-binding site and the hydrophobic pocket of the active site are highly similar in all three proteinases. B. cereus neutral proteinase which is 20 degrees C less thermostable (60 degrees C) than thermolysin (80 degrees C) shows only minor differences in calcium binding sites and salt bridges compared to thermolysin (known from its X-ray diffraction analysis), whereas B. subtilis neutral proteinase (50 degrees C) differs considerably. Therefore it was assumed that the difference in thermostability between B. cereus neutral proteinase and thermolysin is not caused by different metal binding properties, or differences in the active site, but by changes within the rest of the molecule. Calculation of secondary structure potentials according to Chou & Fasman, hydrophobicity and bulkiness of the different structural elements and preferred cold----hot amino-acid residue exchanges indicated, that the thermostability of thermolysin compared to B. cereus neutral proteinase is caused by small effects contributed by numerous amino-acid exchanges distributed over the whole molecule, resulting in increased hydrophobicity of beta-pleated sheet and higher bulkiness of alpha-helical regions. 相似文献
6.
E. B. Bröcker L. Suter B. M. Czarnetzki E. Macher 《Cancer immunology, immunotherapy : CII》1986,23(2):155-157
Summary Previously, we have provided evidence for a positive correlation between HLA-DR expression in primary melanoma and early metastasis [3, 4]. In the present study we investigated whether this relationship was modified by adjuvant BCG immunotherapy. The study comprised 107 patients with a stage I high-risk melanoma; 44 patients had been treated with BCG, whereas the remaining patients had not received any adjuvant therapy. There was no difference in disease-free survival between BCG-treated and untreated patients. Disease-free survival was significantly shorter in patients with high expression of HLA-DR antigens in the primary tumor.Subgrouping BCG-treated and control patients according to HLA-DR phenotype of the melanoma revealed a prolongation of disease-free survival in the subgroup of BCG-treated patients with no or low expression of HLA-DR antigens in the primary melanoma. BCG therapy apparently did not influence prognosis of patients with high expression of HLA-DR antigens in the tumor. 相似文献
7.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
8.
Rearrangement of VHa1-encoding Ig gene segment to the a2 chromosome in an a1/a2 heterozygous rabbit. Evidence for trans recombination 总被引:1,自引:0,他引:1
VDJ genes were cloned from leukemic B cells of an a1/a2 heterozygous Emu-cmyc transgenic rabbit. Restriction mapping and nucleotide sequence analysis indicated that one clone, 5C3, had a VHa1-encoding gene segment functionally rearranged to a JH gene segment from the a2 chromosome. This VDJ gene may be the result of a trans recombination between a VH gene on the a1 chromosome and a JH gene segment on the a2 chromosome or, it may be the result of a cis recombination if the a2 chromosome contains VHa1-encoding gene segments. 相似文献
9.
Christian S. Lobsiger Josef P. Magyar Verdon Taylor Philip Wulf Andrew A. Welcher Amgen EST Program Ueli Suter 《Genomics》1996,36(3):379
The PMP22/EMP/MP20 gene family includes four closely related proteins, peripheral myelin protein-22 (PMP22), epithelial membrane protein-1 (EMP-1), epithelial membrane protein-2 (EMP-2), and epithelial membrane protein-3 (EMP-3), which share amino acid identities ranging from 33 to 43%. In addition, the lens-specific membrane protein MP20 represents a more distant relative. Functionally, this family of proteins is likely to play important roles in the control of cell proliferation, cell differentiation, and cell death. In particular, mutations affecting thePMP22gene are responsible for various hereditary peripheral neuropathies in humans and mice. We report the isolation and characterization of a mouse EMP-1 cDNA and the correspondingemp-1gene. Mouse EMP-1 displays 93% amino acid identity to rat EMP-1 and 39% identity to mouse PMP22. The cDNA-predicted EMP-1 protein contains four putative membrane-associated domains and can beN-linked glycosylatedin vitro.EMP-1 is encoded by a single-copy gene with the positions of introns exactly conserved betweenemp-1andPMP22,corroborating the hypothesis that both genes belong to the same family. Computer-predicted structural domains of EMP-1 are partially mirrored by the exon/intron structure ofemp-1.Most interestingly, exon 4, which covers the potential second transmembrane domain, a small intracellular loop, and half of the third transmembrane domain, encodes the most highly conserved regions between the EMP-1 and PMP22 proteins and is also remarkably conserved in the MP20 gene, indicating some shared functional significance for this module in the PMP22/EMP/MP20 family. 相似文献
10.
The subcellular localization of gamma-glutamyltransferase in calf thymocytes was investigated and compared with that of alkaline phosphodiesterase I, alkaline nitrophenyl phosphatase, succinate-tetrazolium oxidoreductase (succinate-INT reductase) and lactate dehydrogenase after two different methods of cell disruption and differential centrifugation. Most of the activity was recovered in the crude membrane fractions (43.0%), but significant amounts co-pelleted with the large-granule (mitochondria) fractions (31%). The specific activity of the gamma-glutamyltransferase in the purified plasma membrane was 30-50 times that of the enzyme in the cell homogenate and had a similar subcellular distribution to the plasma-membrane markers, alkaline phosphodiesterase I and alkaline nitrophenyl phosphatase. It was concluded that gamma-glutamyltransferase was primary a plasma-membrane-bound enzyme, and that its location in other subcellular fractions was probably due to their contamination with plasma-membrane vesicles. 相似文献