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1.
Markus Pech Thomas Spreter Roland Beckmann Birgitta Beatrix 《The Journal of biological chemistry》2010,285(25):19679-19687
Nascent polypeptide-associated complex (NAC) was identified in eukaryotes as the first cytosolic factor that contacts the nascent polypeptide chain emerging from the ribosome. NAC is present as a homodimer in archaea and as a highly conserved heterodimer in eukaryotes. Mutations in NAC cause severe embryonically lethal phenotypes in mice, Drosophila melanogaster, and Caenorhabditis elegans. In the yeast Saccharomyces cerevisiae NAC is quantitatively associated with ribosomes. Here we show that NAC contacts several ribosomal proteins. The N terminus of βNAC, however, specifically contacts near the tunnel exit ribosomal protein Rpl31, which is unique to eukaryotes and archaea. Moreover, the first 23 amino acids of βNAC are sufficient to direct an otherwise non-associated protein to the ribosome. In contrast, αNAC (Egd2p) contacts Rpl17, the direct neighbor of Rpl31 at the ribosomal tunnel exit site. Rpl31 was also recently identified as a contact site for the SRP receptor and the ribosome-associated complex. Furthermore, in Escherichia coli peptide deformylase (PDF) interacts with the corresponding surface area on the eubacterial ribosome. In addition to the previously identified universal adapter site represented by Rpl25/Rpl35, we therefore refer to Rpl31/Rpl17 as a novel universal docking site for ribosome-associated factors on the eukaryotic ribosome. 相似文献
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Carp myogens of white and red muscles. Properties and amino acid composition of the main low-molecular-weight components of white muscle 总被引:2,自引:2,他引:0
1. The three main components of the 1·5–2s ultracentrifugal peak of carp myogen (white muscle) have been isolated by ammonium sulphate fractionation and zone electrophoresis, and crystallized. 2. The molecular weights of these three proteins were determined by sedimentation and diffusion, by the Archibald method and by amino acid analysis, and found to lie between 9000 and 13000. 3. Their complete amino acid compositions were determined by column chromatography and by their ultraviolet spectra. Both methods revealed abnormal compositions, including the absence of tryptophan and methionine and the presence of large amounts of phenylalanine. At most 1 residue each of tyrosine, cysteine, proline, arginine and histidine was found/molecule. 4. The specific viscosity of component 3 was lower than that of other small globular proteins described so far, a fact that suggests that these proteins approximate more closely to the ideal case of the spherical protein molecule. Also, the presence of a single residue of several amino acids, the absence of disulphide bonds, and the apparent reversibility of denaturation by urea of component 3 suggest that the study of these molecules could provide new information on the structure of proteins. 相似文献
7.
Mohamed Benichou Gracia Martinez-Reina Felix Romojaro Jean-Claude Pech Alain Latché 《Physiologia plantarum》1995,94(4):629-634
A 36-kDa 1-aminocyclopropane-1-carboxylate (ACC) N-malonyltransferase, which converts the ethylene precursor ACC into the conjugated derivative malonyl-ACC (MACC), has been isolated from etiolated mung bean ( Vigna radiata ) hypocotyls, and partially purified in a four-step procedure. The enzyme is stimulated about 7-fold by 100 m M K+ salts or 0.5 m M Co2+ salts, and is inhibited competitively by D-phenylalanine (Ki = 1.3 m M ) and non competitively by CoASH (0.3 m M ). Beside malonyl-CoA, it is capable to use succinyl-CoA as an acyl donor. The 36-kDa enzyme described here exhibits a lower optimum temperature (40°C) and a 7- or 3-fold lower apparent Km for ACC (68 μ M ) and malonyl-CoA (74 μ M ), respectively, when compared with its 55 kDa isoform already isolated from the same plant material. This data support the idea that several isoforms of ACC N-malonyltransferase exist in plants. These isoforms may play a differential role in regulating the availability of ACC, and consequently the rate of ethylene production, as well as detoxifying cells from D-amino acids. 相似文献
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Immunoglobulin genes of different subgroups are interdigitated within the VK locus 总被引:30,自引:6,他引:24
The variable regions of immunoglobulins are encoded by multigene families which are rearranged during B-cell differentiation. These families were classified in groups and subgroups based on their amino acid sequences. Genes belonging to a distinct subgroup are believed to occur in the genome within clusters. We are investigating the organization of human variable region genes of the kappa type (VK genes, ref. 1) in the germline and found now for the first time that VK sequences of three of the four different subgroups are interdigitated within the VK locus. We present evidence for the interspersion of two VKIII genes and a VKII pseudogene within an array of five VKI genes. All eight VK sequences are arranged in the same orientation. An evolutionary model for the generation of this 'mixed cluster' is discussed. 相似文献
9.
J Meirion Thomas W H Redding R C Coombes J P Sloane H T Ford J-C Gazet T J Powles 《BMJ (Clinical research ed.)》1978,2(6131):157-159
Two studies were performed to assess the accuracy of non-invasive methods in detecting intra-abdominal metastases from breast cancer. Firstly, the sites of spread detected at the time of first presentation with metastases were compared with the sites of spread shown at necropsy in the same patients. Although about two-thirds of the patients with bone and lung metastases at necropsy had had metastases detected at these sites when they first presented with metastases, only a third of the patients with liver metastases and none of those with other intra-abdominal metastases had had evidence of disease at first presentation with metastases. The second study confirmed a poor detection rate of liver and other intra-abdominal metastases in patients with breast cancer undergoing laparotomy and oophorectomy who were staged immediately before operation.Pre-mastectomy staging laparotomy should be considered in those patients with primary breast cancer who are most likely to have disseminated disease beyond the regional nodes. In the presence of occult gross metastases detected by staging laparotomy, mastectomy will not provide additional protection against loca recurrence of disease. Patients with occult gross metastases should also be excluded from studies on adjuvant chemotherapy (designed to treat micrometastases). Aggressive methods of staging are justified to protect the patient as far as possible against unnecessary mastectomy and to identify those patients who should be treated by therapeutic chemotherapy rather than adjuvant chemotherapy. 相似文献
10.
Fractionation of charge-modified low density lipoproteins by fast protein liquid chromatography. 总被引:1,自引:0,他引:1
B Vedie I Myara M A Pech J C Maziere C Maziere A Caprani N Moatti 《Journal of lipid research》1991,32(8):1359-1369
We describe a methodology developed to separate different forms of charge-modified low density lipoproteins (LDL) using the fast protein liquid chromatography (FPLC) system from Pharmacia. Lipoproteins were isolated by sequential ultracentrifugation and introduced onto an anion-exchange column (Mono Q HR 5/5). The multistep NaCl gradient elution was optimized and the analytical variables were determined on copper-oxidized LDL. After oxidation by copper for various times (up to 48 h), five forms were obtained (fractions A, B, C, D, and E). Within-run and day-to-day reproducibility were better than 8.6% and 10%, respectively. Protein and cholesterol recovery after the chromatographic separation was good (greater than 82%) and the detection limit was about 1 microgram. The more negative forms of collected LDL were mainly characterized by an increase in the lipid peroxidation product content, a depletion of vitamin E, an alteration of apoB and increased degradation by macrophages. The proposed methodology was applied to the study of LDL modifications generated by human umbilical endothelial cells and the protective effect of antioxidants (vitamin E and probucol). 相似文献