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11.
Binding of BiP to an assembly-defective protein in plant cells 总被引:5,自引:1,他引:4
Emanuela Pedrazzini Giovanna Giovinazzo Roberto Bollini Aldo Ceriotti Alessandro Vitale 《The Plant journal : for cell and molecular biology》1994,5(1):103-110
The binding protein (BiP) has been implicated as a mediator of protein folding and assembly in the endoplasmic reticulum of mammalian cells and has often been found in stable association with structurally defective proteins. To acquire information on the activity of BiP in plant cells, we have expressed in tobacco protoplasts the wild type form and an assembly-defective form of bean phaseolin. Phaseolin (PHSL) is a soluble, trimeric, storage glycoprotein co-translationally inserted into the lumen of the endoplasmic reticulum and then transported along the secretory pathway to the protein storage vacuoles. We have previously shown that a PHSL mutant in which the last 59 amino acids have been deleted (Δ363PHSL) is unable to form trimers and is retained in a pre-Golgi compartment when synthesized in Xenopus oocytes. When transiently expressed in tobacco leaf protoplasts, wild-type PHSL is correctly glycosylated and assembles efficiently and rapidly into trimers. Δ363PHSL is also correctly glycosylated but does not trimerize. Tobacco BiP and Δ363PHSL are co-immunoselected using either anti-PHSL or anti-BiP antibodies. Under the same conditions, co-immunoselection of BiP with wild-type PHSL is not detectable. The BiP bound to Δ363PHSL can be released by treatment of the complex with ATP, indicating that the binding is related to the proposed function of BiP in protein folding and assembly in the endoplasmic reticulum. These data indicate that BiP stably binds structurally defective proteins in plant cells. 相似文献
12.
Giovanna Berruti 《Molecular reproduction and development》1994,38(4):386-392
The majority of cellular responses to changing environmental conditions is regulated by protein kinases. Spermatozoa have many special properties, including motility with demonstrated chemotaxis, the ability to undergo capacitation, and the acrosome reaction, which are in part controlled by extracellular signals and in which sperm kinases are considered to be involved. We have previously reported that there is a protein kinase activity, which phosphorylates the synthetic substrate poly-(Glu, Tyr) with a Km value of 2.3 μM, and is inhibited by the tyrosine kinase inhibitor tyrphostin, in the protein extract from boar spermatozoa (Berruti and Porzio, 1992: Biochim Biophys Acta 1118:149–154). Now we have demonstrated that the enzyme is cytosolic, is active as a monomer of Mr 42,000, is stimulated by Mg2+ > Mn2+ but not by Ca2+, is renaturable, and can phosphorylate native protein substrates such as microtubule-associated protein 2 (MAP2) and histone H2B both on the tyrosine and serine residues. N-terminal sequence analysis suggests that it is a novel protein. These new findings imply that the boar sperm 42 kD kinase may be a novel member of the emerging class of dual-specificity protein kinases, and they raise the intriguing question of its function in the protein kinase network mediating signal transduction in mammalian spermatozoa. © 1994 Wiley-Liss, Inc. 相似文献
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Giovanna Belmonte Cecilia Pederzolli Peter Maček Gianfranco Menestrina 《The Journal of membrane biology》1993,131(1):11-22
Summary The interaction ofActinia equina equinatoxin II (EqT-II) with human red blood cells (HRBC) and with model lipid membranes was studied. It was found that HRBC hemolysis by EqT-II is the result of a colloid-osmotic shock caused by the opening of toxin-induced ionic pores. In fact, hemolysis can be prevented by osmotic protectants of adequate size. The functional radius of the lesion was estimated to be about 1.1 nm. EqT-II increased also the permeability of calcein-loaded lipid vesicles comprised of different phospholipids. The rate of permeabilization rised when sphingomyelin was introduced into the vesicles, but it was also a function of the pH of the medium, optimum activity being between pH 8 and 9; at pH 10 the toxin became markedly less potent. From the dose-dependence of the permeabilization it was inferred that EqT-II increases membrane permeability by forming oligomeric channels comprising several copies of the cytolysin monomer. The existence of such oligomers was directly demonstrated by chemical cross-linking. Addition of EqT-II to one side of a planar lipid membrane (PLM) increases the conductivity of the film in discrete steps of defined amplitude indicating the formation of cation-selective channels. The conductance of the channel is consistent with the estimated size of the lesion formed in HRBC. High pH and sphingomyelin promoted the interaction even in this system. Chemical modification of lysine residues or carboxyl groups of this protein changed the conductance, the ion selectivity and the current-voltage characteristic of the pore, suggesting that both these groups were present in its lumen. 相似文献
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Leirla Salazar Hafida Fsihi Edda de Rossi Giovanna Riccardi Carmen Rios Stewart T. Cole Howard E. Takiff 《Molecular microbiology》1996,20(2):283-293
The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae. 相似文献
17.
Early in development the precursors of germ cells in Drosophila migrate at the posterior pole of the embryo and translocate to the bottom of the developing posterior midgut primordium. At the end of germ band elongation the pole cells cross the gut wall to enter in association with the gonadal mesoderm. We used laser scanning confocal microscopy on whole-mount Rh-phalloidin-stained embryos and transmission electron microscopy to investigate how pole cells cross the epithelial wall of the posterior midgut primordium. Our results suggest that pole cells leave the midgut sac by traveling through the intercellular spaces of the epithelium. During this process the epithelial cells at the bottom of the posterior midgut primordium are greatly deformed, but their junctional complexes do not completely release, avoiding breaks in the epithelial wall. 相似文献
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19.
Age-dependent population diffusion with external constraint 总被引:3,自引:0,他引:3
We present a simple model for age dependent population diffusion when the dynamics is submitted to external constraints. Existence, uniqueness and dependence on the parameters of the solution are discussed.This work has been done within the framework of the cultural agreement between the Universities of Bordeaux and Rome 相似文献
20.
Floriano Papi Giovanna Mariotti Augusto Foa' Vittorio Fiaschi 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1980,135(3):227-232
Summary Test releases performed at five symmetrically arranged sites around the loft, at a distance of 78–99 km from it, showed that 1) anosmatic birds transported without alteration of the earth's magnetic field were completely random-oriented, 2) anosmatic birds transported in a container inside which the intensity of the magnetic field was strongly reduced were unable to orientate homewards and mostly departed according to a preferred compass direction, 3) control birds, which could smell, and were transported without alteration of the magnetic field, were homeward oriented and performed better in homing than both experimental groups. The conclusion is that anosmatic birds are unable to detect home direction at unfamiliar sites and that magnetic stimuli perceived during the outward journey are unable to substitute olfactory cues.Abbreviation
PCD
preferred compass direction
Supported by a grant from the Consiglio Nazionale delle Ricerche 相似文献