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31.
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
32.
Summary There is a protease, which is activated by Ca2+ (about 100 M), works at neutral pH and exists in the cytoplasm inChara australis. This protease may correspond to calpain, the calcium-activated neutral protease, which has been studied in animal cells. This is the first report showing the existence of a calcium-activated protease in plant cells. 相似文献
33.
N-Terminal Sequence of Pig Brain Choline Acetyltransferase Purified by a Rapid Procedure 总被引:6,自引:5,他引:1
Axel Braun Yves-Alain Barde Friedrich Lottspeich Werner Mewes Hans Thoenen 《Journal of neurochemistry》1987,48(1):16-21
A procedure is reported that allows the purification and amino terminal sequencing of pig brain choline acetyltransferase. The enzyme (present in extremely low amounts in this tissue) is eluted together with its antibody from an affinity column by a mild pH shift and the resulting enzyme-antibody complex separated by gel electrophoresis. The band corresponding to the enzyme is electroeluted from the gel using volatile solutions allowing the direct determination of the amino acid composition and partial sequence. The first 11 residues are: Pro-Ile-Leu-Glu-Lys-Thr-Pro-Pro-Lys-Met-Ala. 相似文献
34.
Mella Adlersberg Kuo-Peing Liu Shu-Chi Hsiung Yigal Ehrlich Hadassah Tamir 《Journal of neurochemistry》1987,49(4):1105-1115
The endogenous phosphorylation of serotonin binding protein (SBP), a soluble protein found in central and peripheral serotonergic neurons, inhibits the binding of 5-hydroxytryptamine (5-HT, serotonin). A protein kinase activity that copurifies with SBP (SBP-kinase) was partially characterized and compared with calcium/calmodulin-dependent protein kinase II (CAM-PK II). SBP itself is not the enzyme since heating destroyed the protein kinase activity without affecting the capacity of the protein to bind [3H]5-HT. SBP-kinase and CAM-PK II kinase shared the following characteristics: (1) size of the subunits; (2) autophosphorylation in a Ca2+-dependent manner; and (3) affinity for Ca2+. In addition, both forms of protein kinase phosphorylated microtubule-associated proteins well and did not phosphorylate myosin, phosphorylase b, and casein. Phorbol esters or diacylglycerol had no effect on either of the protein kinases. However, substantial differences between SBP-kinase and CAM-PK II were observed: (1) CAM enhanced CAM-PK II activity, but had no effect on SBP-kinase; (2) synapsin I was an excellent substrate for CAM-PK II, but not for SBP-kinase; (3) 5-HT inhibited both the autophosphorylation of SBP-kinase and the phosphorylation of SBP, but had no effect on CAM-PK II. These data indicate that SBP-kinase is different from CAM-PK II. Phosphopeptide maps of SBP and SBP-kinase generated by digestion with S. aureus V8 protease are consistent with the conclusion that these proteins are distinct molecular entities. It is suggested that phosphorylation of SBP may regulate the transport of 5-HT within neurons. 相似文献
35.
In vitro stimulation of intact rat posterior pituitary by either veratridine or K+ depolarization results in the concomitant release of neurophysins and in a decrease (70-80%) in their carboxyl methylation as measured either with L-[methyl-3H]methionine in the intact lobes after stimulation or in their homogenates with [methyl-3H]S-adenosyl-L-methionine and purified protein carboxyl methyltransferase. A similar reduction in neurophysin methylation (60%) was observed when the arrival of newly synthesized neurophysins at the posterior pituitary was blocked by colchicine. Experimental data indicate that the reduction in neurophysin content of the lobes after 12 h of colchicine treatment (less than 7%) or after in vitro stimulation (about 10%) cannot account for the marked reduction in neurophysin methylation. The results suggest that the granule pool characterized by rapid turnover of neurophysins probably represents the major source of methyl acceptor proteins in the lobe. In spite of the marked reduction in neurophysin methyl accepting capacity observed after stimulation, there was no parallel increase in methyl accepting capacity of the released neurophysins. We propose that a neurophysin subfraction that might be associated with the membrane of releasable granules participates in the methylation reaction in situ. 相似文献
36.
A similar protein portion for two exoglucanases secreted by Saccharomyces cerevisiae 总被引:4,自引:0,他引:4
Exoglucanase (exo-1,3-β-D-glucan glycohydrolase, EC 3.2.1.56) activity secreted by Saccharomyces cerevisiae into the culture medium was separated by ion exchange chromatography into two glycoprotein isoenzymes which contributed 10%
(exoglucanase I) and 90% (exoglucanase II) towards the total activity. Analysis of the “in vitro” deglycosylated products
by polyacrylamide gel electrophoresis under native or denaturing conditions indicated that the protein portions of both exoglucanases
exhibited identical mobility, each one consisting of two polypeptides with M
r of 47000 and 48000. The same profile was shown by the exoglucanase secreted in the presence of tunicamycin. Antibodies raised
against the protein portion of exoglucanase II did react with both native exoglucanases and their deglycosylated products
with a pattern indicative of immunological identity. Digestion of the “in vitro” deglycosylated products of both exoglucanases
with Staphylococcus aureus V-8 protease or trypsin generated the same proteolytic fragments in each case. Only exoglucanase II was secreted by protoplasts.
These and previously reported results indicate that the protein portions of both isoenzymes may be the product of the same
gene (or a family of related genes), and that exoglucanase I is a product of enzyme II, modified by a process occurring beyond
the permeability barrier of the cell. 相似文献
37.
The Goodwin and Trainor model of pattern generation in calcium-regulated strain fields is studied in the case where calcium input and calcium output processes are involved. It is shown that the properties of the original model may still remain provided that the input-output processes are not unstable. In this last case, despite the eventual stabilizing effect of the calcium exchange term, perturbations of the generalized system can grow and lead to inhomogeneous solutions. Applications to cell differentiation and cell growth are discussed. 相似文献
38.
Protein phosphorylation in Streptomyces albus 总被引:1,自引:0,他引:1
Z. Dobrová M. Jirsová T. Petík P. Ryavý J. Náprstek J. Janeek 《FEMS microbiology letters》1990,71(1-2):145-148
The phosphorylated proteins of Streptomyces albus, radioactively labeled with [32P]orthophosphate have been analyzed by gel electrophoresis and autoradiography. More than 10 protein species were found to be phosphorylated. With [32P]ATP as substrate cell free extracts phosphorylated endogenous proteins in vitro which were predominantly phosphorylated in vivo. From cell extract which exhibited active phosphorylated in vitro, a protein kinase has been partially purified. The kinase activity was identified in fractions corresponding to a 90 kDa protein. 相似文献
39.
A system for the inducible secretion of proteins from Bacillus subtilis during logarithmic growth 总被引:1,自引:0,他引:1
Alex Edelman Gwennaël Joliff ré Klier Georges Rapoport 《FEMS microbiology letters》1988,52(1-2):117-120
Abstract A Bacillus subtilis-Escherichia coli shuttle vector was constructed containing the B. subtilis levansucrase gene promoter and region encoding its signal sequence.
A site for the restriction enzyme Nae I was included to facilitate precise translational fusions to the DNA encoding the levansucrase signal sequence. Fusions of TEM β-lactamase to this construct displayed sucrose-inducible expression and secretion of B. subtilis . 相似文献
A site for the restriction enzyme Nae I was included to facilitate precise translational fusions to the DNA encoding the levansucrase signal sequence. Fusions of TEM β-lactamase to this construct displayed sucrose-inducible expression and secretion of B. subtilis . 相似文献
40.
Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1
Alicia Bravo Sagrario Ortega Gertrudis de Torrontegui Ramón Díaz 《Molecular & general genetics : MGG》1988,215(1):146-151
Summary The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed. 相似文献