51 research outputs found
Oxygen binding and slow structural changes in chlorocruorin from Spirographis spallanzanii.
No full textA ribosomal protein is specifically recognized by saporin, a plant toxin which inhibits protein synthesis.
No full textAbstractMany plants express enzymes which specifically remove an adenine residue from the skeleton of the 28 S RNA in the major subunit of the eukaryotic ribosome (ribosome inactivating proteins, RIPs). The site of action of RIPs (A4324 in the rRNA from rat liver) is in a loop structure whose nucleotide sequence all around the target adenine is also conserved in those species which are completely or partially insensitive to RIPs. In this paper we identify a covalent complex between saporin (the RIP extracted from Saponaria officinalis) and ribosomal proteins from yeast (Saccharomyces cerevisiae), by means of chemical crosslinking and immunological or avidin-biotin detection. The main complex (mol. wt. ≈ 60 kDa) is formed only with a protein from the 60 S subunit of yeast ribosomes, and is not detected with ribosomes from E. coli, a resistant species. This observation supports the hypotesis for a molecular recognition mechanism involving one or more ribosomal proteins, which could provide a ‘receptor’ site for the toxin and favour optimal binding of the target adenine A4324 to the active site of the RIP
The crystal structure of saporin SO6 from Saponaria officinalis and its interaction with the ribosome
No full textThe 2.0 Angstrom resolution crystal structure of the ribosome inactivating protein saporin (isoform 6) from seeds of Saponaria officinalis is presented. The fold typical of other plant toxins is conserved, despite some differences in the loop regions. The loop between strands beta 7 and beta 8 in the C-terminal region which spans over the active site cleft appears shorter in saporin, suggesting an easier access to the substrate. Furthermore,ve investigated the molecular interaction between saporin and the yeast ribosome by differential chemical modifications. A contact surface inside the C-terminal region of saporin has been identified. Structural comparison between saporin and other ribosome inactivating proteins reveals that this region is conserved and represents a peculiar motif involved in ribosome recognition. (C) 2000 Federation of European Biochemical Societies
ANALYSIS OF BIOCHEMICAL PROCESSES IN SINGLE LIVING CELLS BY QUANTITATIVE MICROSCOPY
No full textSpectroscopic measurements in single living cells are made possible by the development of computer controlled light detectors, which, when applied to optical microscopes, yield spatial, temporal and eventually spectroscopic information about the sample. This minireview describes some experiments in which the distribution and concentration of specific intracellular markers (proteins, protein complexes, RNA) has been followed by quantitative microscopy. The examples chosen have contributed to shed light on a biochemical process as it happens in vivo; because of the non ideal conditions of the intracellular milieu, the comparison of in vivo and in vitro experiments is of great relevance to the understanding of cellular physiology
Evaluation of different extraction methods from pomegranate whole fruit or peels and the antioxidant and antiproliferative activity of the polyphenolic fraction
No full textPomegranate is a functional food of great interest, due to its multiple beneficial effects on human health. This fruit is rich in anthocyanins and ellagitannins, which exert a protective role towards degenerative diseases. The aim of the present work was to optimize the extraction procedure, from different parts of the fruit, to obtain extracts enriched in selected polyphenols while retaining biological activity. Whole fruits or peels of pomegranate cultivars, with different geographic origin, were subjected to several extraction methods. The obtained extracts were analyzed for polyphenolic content, evaluated for antioxidant capacity and tested for antiproliferative activity on human bladder cancer T24 cells. Two different extraction procedures, employing ethyl acetate as a solvent, were useful in obtaining extracts enriched in ellagic acid and/or punicalagins. Antioxidative and antiproliferative assays demonstrated that the antioxidant capability is directly related to the phenolic content, whereas the antiproliferative activity is to be mainly attributed to ellagic acid
Chromane derivatives of small aromatic molecules: Chemoenzymatic synthesis and growth inhibitory activity on human tumor cell line LoVo WT
No full textAromatic substrates tyrosol (p-hydroxyphenylethanol) and 2,6-dihydroxynaphthalene (2,6-DHN) were converted into chromane derivatives by means of chemoenzymatic reactions catalyzed by the aromatic prenyltransferase of bacterial origin NovQ, using dimethylallyl bromide as allylic substrate instead of the natural isoprenyl pyrophosphate substrate. Stereoselective prenylation occurred in o-position with respect to the phenol hydroxyl in both compounds. Prenylated derivatives were readily converted into chromane products via a selective 6-endo-trig cyclization involving the oxygen atom from the phenol moiety and the double bond of the prenyl substituent, a process catalyzed by FeCl(3). These findings set up the basis of a most convenient two-step, one-pot process which allows for easy recovery of the chromane products in high yields. The chromane derivatives thus obtained were tested for cytotoxicity and pro-apoptotic activity using LoVo WT cells, a line of human colon adenocarcinoma. (C) 2009 Elsevier Ltd. All rights reserved
Crystallization and preliminary X-ray study of Saporin, a Ribosome Inactivating Protein from Saponaria officinalis
No full textSingle crystals of the protein saporin isolated from the seeds of S. officinalis have been grown by the vapor-diffusion method using ammonium sulfate as precipitant. The crystals are tetragonal, space group P4(1)22 (P4(3)22), with cell-dimensions a = b = 67.53 and c = 119.67 Angstrom, and diffract to 2.0 Angstrom resolution on a rotating-anode X-ray source. The asymmetric unit contains one molecule, corresponding to a volume of the asymmetric unit per unit mass (V-m) of 2.38 Angstrom(3) Da(-1)
Modulation of mitochondrial respiration by nitric oxide: investigation by single cell fluorescence microscopy
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