66,795 research outputs found
Ancestry and evolution of a secretory pathway serpin
No full textKumar A, Ragg H. Ancestry and evolution of a secretory pathway serpin. BMC Evolutionary Biology. 2008;8(1): 250.Background:The serpin (serine protease inhibitor) superfamily constitutes a class of functionally highly diverse proteins usually encompassing several dozens of paralogs in mammals. Though phylogenetic classification of vertebrate serpins into six groups based on gene organisation is well established, the evolutionary roots beyond the fish/tetrapod split are unresolved. The aim of this study was to elucidate the phylogenetic relationships of serpins involved in surveying the secretory pathway routes against uncontrolled proteolytic activity. Results: Here, rare genomic characters are used to show that orthologs of neuroserpin, a prominent representative of vertebrate group 3 serpin genes, exist in early diverging deuterostomes and probably also in cnidarians, indicating that the origin of a mammalian serpin can be traced back far in the history of eumetazoans. A C-terminal address code assigning association with secretory pathway organelles is present in all neuroserpin orthologs, suggesting that supervision of cellular export/import routes by antiproteolytic serpins is an ancient trait, though subtle functional and compartmental specialisations have developed during their evolution. The results also suggest that massive changes in the exon-intron organisation of serpin genes have occurred along the lineage leading to vertebrate neuroserpin, in contrast with the immediately adjacent PDCD10 gene that is linked to its neighbour at least since divergence of echinoderms. The intron distribution pattern of closely adjacent and co-regulated genes thus may experience quite different fates during evolution of metazoans. Conclusion: This study demonstrates that the analysis of microsynteny and other rare characters can provide insight into the intricate family history of metazoan serpins. Serpins with the capacity to defend the main cellular export/import routes against uncontrolled endogenous and/or foreign proteolytic activity represent an ancient trait in eukaryotes that has been maintained continuously in metazoans though subtle changes affecting function and subcellular location have evolved. It is shown that the intron distribution pattern of neuroserpin gene orthologs has undergone substantial rearrangements during metazoan evolution
Multiple gains of spliceosomal introns in a superfamily of vertebrate protease inhibitor genes
No full textRagg H, Kumar A, Köster K, et al. Multiple gains of spliceosomal introns in a superfamily of vertebrate protease inhibitor genes. BMC Evolutionary Biology. 2009;9(1):208.Background: Intron gains reportedly are very rare during evolution of vertebrates, and the mechanisms underlying their creation are largely unknown. Previous investigations have shown that, during metazoan radiation, the exon-intron patterns of serpin superfamily genes were subject to massive changes, in contrast to many other genes. Results: Here we investigated intron dynamics in the serpin superfamily in lineages pre- and postdating the split of vertebrates. Multiple intron gains were detected in a group of ray-finned fishes, once the canonical groups of vertebrate serpins had been established. In two genes, cooccurrence of non-standard introns was observed, implying that intron gains in vertebrates may even happen concomitantly or in a rapidly consecutive manner. DNA breakage/repair processes associated with genome compaction are introduced as a novel factor potentially favoring intron gain, since all non-canonical introns were found in a lineage of ray-finned fishes that experienced genomic downsizing. Conclusion: Multiple intron acquisitions were identified in serpin genes of a lineage of ray-finned fishes, but not in any other vertebrates, suggesting that insertion rates for introns may be episodically increased. The co-occurrence of non-standard introns within the same gene discloses the possibility that introns may be gained simultaneously. The sequences flanking the intron insertion points correspond to the proto-splice site consensus sequence MAG↑N, previously proposed to serve as intron insertion site. The association of intron gains in the serpin superfamily with a group of fishes that underwent genome compaction may indicate that DNA breakage/repair processes might foster intron birth
Association Constants for Metal Hexacyanide Binding to Cytochrome c
No full textThe binding of [Co(CN)6]3-, and that of [Fe(CN)6]3- and [Ru(CN)6]4- using a competitive method, to horse cytochrome c has been studied by 59Co NMR spectroscopy. At I = 0.07 M, without added salt and in 2H2O at pH* 7.3 (measured in 2H2O) and 25 degrees C, there are at least two binding sites on ferricytochrome c and ferrocytochrome c for [Co(CN)6]3-. Association constants were determined to be 2.0 +/- 0.6 X 10(3) M-1 and 1.5 +/- 0.5 X 10(2) M-1, respectively, with no effect of the oxidation state of the cytochrome. At higher ionic strength (I = 0.12 M) adjusted with KCl the binding markedly decreased, and, although it was not possible to determine the precise binding stoichiometry and magnitude of association constants, it is clear that the association constants are less than or equal to 1.5 X 10(2) M-1. The binding of [Ru(CN)6]4- at I = 0.07, without added salt and in 2H2O at pH* 7.3 and 23 degrees C, was not precisely defined, but its binding strength relative to that of [Fe(CN)6]3- was determined. Extrapolating this to I = 0.12 (KCl) suggests that under these conditions the association constant for [Ru(CN)6]4- binding to ferricytochrome c is less than or equal to 3 X 10(2) M-1
Modifiche delle proprietà delle macromolecole di grano saraceno a seguito di diversi trattamenti tecnologici
No full textExpression of human antithrombin III in Saccharomyces cerevisiae and Schizosaccharomyces pombe
No full textBröker M, Ragg H, Karges HE. Expression of human antithrombin III in Saccharomyces cerevisiae and Schizosaccharomyces pombe. Biochim. Biophys. Acta. 1987;908:203-213
Elettrocatalizzatori esenti da platino per la reazione di riduzione di ossigeno
No full textAd oggi il platino e le sue leghe sono i migliori catalizzatori per la riduzione di ossigeno nelle pile a combustibile PEM. Poiché però il metallo è scarso e costoso, è in atto un grosso sforzo per trovare dei materiali catalitici basati su metalli non preziosi. Catalizzatori a base N-Fe e N-Co sembrano essere alternative promettenti [1]. Inoltre, la letteratura mette in evidenza l’importanza della natura e delle proprietà chimico-fisiche dei carboni usati come supporti. Un miglioramento delle prestazioni dei carboni è auspicabile. Tra le possibilità studiate sono da considerare le modificazioni della natura e densità superficiale dei gruppi funzionali nativi e l’introduzione di eteroatomi e di centri metallici.
In questo lavoro presentiamo alcuni risultati della reazione di riduzione di ossigeno su carboni attivi modificati per trattamento con ammine e con centri metallici (Co, Fe). Come sorgenti di azoto sono state usate - diammine e triammine. La caratterizzazione e’ stata condotta mediante metodi chimico-fisici (XPS, Multinuclear Solid State NMR) ed elettrochimici. I risultati ottenuti mostrano l’influenza della natura del precursore azotato e dei centri metallici sul comportamento ORR dei catalizzatori.
[1] F. Charreteur, F. Jaouen, S. Ruggeri, J.-P. Dodelet, Electrochim. Acta, 53 (2008) 2925
Kinetics of electron transfer between mitochondrial cytochrome c and iron hexacyanides
No full textThe reduction of horse and Candida krusei cytochromes c by ferrocyanide has been studied by 1H NMR spectroscopy and the reaction found to involve a precursor complex of ferrocyanide bound to ferricytochrome c (pH* 7.4, 2H2O, I = 0.12, and 25 degrees C). The electron transfer rate constants for the reduction of the two ferricytochromes by associated ferrocyanide were found to be the same at 780 +/- 80 sec-1 but the association constants for binding of ferrocyanide to ferricytochrome c were significantly different: horse, 90 +/- 20 M-1 and Candida, 285 +/- 30 M-1. The different association constants partly accounts for the previously observed reactivity difference between horse and Candida cytochromes c. Comparison of the NMR data with data obtained by other kinetic methods has allowed the electron transfer rate constant for the oxidation of ferrocytochrome c by associated ferricyanide to be determined. This was found to be 4.6 +/- 1 X 10(4) sec-1
Response to Anoxia in Rice and Wheat Seedlings: Changes in the pH of Intracellular Compartments, Glucose-6-Phosphate Level, and Metabolic Rate
No full text31P nuclear magnetic resonance spectroscopy was used to measure intracellular pH in living tissues. Oxygen deprivation caused fast cytoplasmic acidification from pH 7.4 to 7.0 in shoots of rice, Oryza sativa L. var arborio, a species highly resistant to anoxia. Acidification was complete after 10 minutes of anoxia. Alkalinization of both cytosplasm and vacuole followed thereafter. In the anoxia intolerant wheat shoots, Triticum aestivum L. var MEK, the same treatment caused a sharper cytoplasmic acidification, from pH 7.4 to 6.6, which occurred during a period of 2 hours. Cytoplasmic acidification continued with progress of anoxia and there was no vacuolar alkalinization comparable to the one observed in rice. In wheat oxyen, withdrawal also caused the reduction of both glucose-6-phosphate level and of metabolic rate. It also induced heavy losses of inorganic phosphate from tissues. Conversely, in rice, glucose-6-phosphate level and metabolic rate were increased and inorganic phosphate leakage from tissues was completely absent. These results are discussed in relation to the mechanisms of plant resistance to anoxia
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