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1.
R.J. Ulvik I. Romslo F. Roland R.R. Crichton 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,677(1):50-56
Mitochondria mobilize iron from ferritin by a mechanism that depends on external FMN. With rat liver mitochondria, the rate of mobilization of iron is higher from rat liver ferritin than from horse spleen ferritin. With horse liver mitochondria, the rate of iron mobilization is higher from horse spleen ferritin than from rat liver ferritin. The results are explained by a higher affinity between mitochondria and ferritins of the same species. The mobilization of iron increases with the iron content of the ferritin and then levels off. A maximum is reached with ferritins containing about 1 200 iron atoms per molecule. The results represent further evidence that ferritin may function as a direct iron donor to the mitochondria. 相似文献
2.
The seasonal chronology of the events of the reproductive cycle, and changes in the structure and function of the primary and accessory organs of the male bent-winged bat, Miniopterus schreibersii, were studied at latitude 37 degrees S in temperate southeastern Australia. The testicular cycle commenced in late spring (November), and sperm appeared in the seminiferous tubules and epididymides in early fall (March). The cycle of the accessory sex gland complex generally paralleled the testicular cycle, reaching maximum hypertrophy at the time of insemination in late fall (April/May). Thereafter, the primary and secondary sex glands (except the ampullary gland) involuted as the animals entered winter torpor. However, a cauda epididymal store of sperm persisted until late spring, and sperm were often observed, as well, in the ampullary gland duct and alveoli throughout winter. This study has confirmed that male Miniopterus differs from other vespertilionids in that accessory gland activity declines following the fall breeding in keeping with the fact that, unlike in other vespertilionids, insemination, ovulation and conception are concurrent events in the fall in this species. The reduced secretory status of the Leydig cells and exceptionally low levels of circulating androgens throughout the year, in combination with the presence of viable epididymidal sperm for most of gestation, are all interesting features of this reproductive cycle. 相似文献
3.
4.
The immobilization of pullulanase and beta-amylase on soluble polysaccharides (dextrans and amylose) has been carried out. The method used for coupling the enzymes to the carbohydrate support involves limited periodate oxidation of the polysaccharide followed by reductive alkylation with sodium cyanoborohydride or borohydride. The influence of the degree of functionalization of the carbohydrate, the incubation time, the nature of the reducing agent and, for the dextrans studied, their molecular weight, on the properties of the conjugate were studied. We have observed an apparent correlation between the molecular weight of the glycoprotein conjugates formed and their thermal stability, resistance to urea denaturation and their kinetic parameters. By selecting the proper experimental conditions leading to conjugates with maximum thermal stabilities, it has also been shown that beta-amylase conjugates can hydrolyze starch at a temperature 20 degrees C higher than the corresponding value for the native enzyme. This result demonstrates that conjugation may result in modified enzymes leaving a high operational stability at elevated temperatures. We suggest that the immobilization method presented in this article represents an approach to the stabilization of enzymes employed at an industrial level, which may be of general application. 相似文献
5.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
6.
Reductive alkylation of ribosomes as a probe to the topography of ribosomal proteins 总被引:3,自引:1,他引:2
Escherichia coli ribosomes were treated with a number of different aldehydes of various sizes in the presence of NaBH(4). After incorporation of either (3)H or (14)C, the ribosomal proteins were separated by two-dimensional polyacrylamide-gel electrophoresis and the extent of alkylation of the lysine residues in each protein was measured. The same pattern of alkylation was observed with the four reagents used, namely formaldehyde, acetone, benzaldehyde and 3,4,5-trimethoxybenzaldehyde. Every protein in 30S and 50S subunits was modified, although there was considerable variation in the degree of alkylation of individual proteins. A topographical classification of ribosomal proteins is presented, based on the degree of exposure of lysine residues. The data indicate that every protein of the ribosome has at least one lysine residue exposed at or near the surface of the ribonucleo-protein complex. 相似文献
7.
Iron metabolism--new perspectives in view. 总被引:5,自引:0,他引:5
8.
B. Gallois Béatrice Langlois d'Estaintot Marie-Anges Michaux Alain Dautant Thierry Granier Gilles Précigoux José-Antonio Soruco Francine Roland Octavío Chavas-Alba Adelina Herbas Robert R. Crichton 《Journal of biological inorganic chemistry》1997,2(3):360-367
The X-ray structure of recombinant horse L-chain (rL) apoferritin, solved at 2.0?Å resolution with a final R factor of 17.9%, gives evidence that the residue at position 93 in the sequence is a proline and not a leucine, as found in earlier sequencing studies. The structure is isomorphous with other apoferritin structures, and we thus draw particular attention to those structural features which can be related to the stability and function of the protein. Analysis of hydrogen bonding and salt bridge interactions shows that dimers and tetramers are the most stable molecular entities within the protein shell: a result confirming earlier biophysical experiments. The stability of horse rL apoferritin to both dissociation into subunits at acidic pH values and to complete unfolding in guanidine chloride solutions is compared with that of other apoferritins. This emphasizes the role played by the salt bridge in the stability of this protein family. The horse rL apoferritin is significantly more resistant to denaturation than horse spleen ferritin, which in turn is more resistant than any human rH apoferritins, even those for which a salt bridge is restored. Finally, this structure determination not only establishes that a preformed pocket exists in L-chain apoferritin, at a site known to be able to bind porphyrin, but also underlines the particular function of a cluster of glutamic acids (E53, E56, E57 and E60) located at the entrance of this porphyrin-binding pocket. 相似文献
9.
Robert R. Crichton Francoise Roman Francine Roland 《Journal of inorganic biochemistry》1980,13(4):305-316
The release of iron from horse spleen ferritin by the chelating agents desferrioxamine B, rhodotorulic acid, 2,3-dihydroxybenzoate, 2,2′-bipyridyl and pyridine-2-aldehyde-2-pyridyl hydrazone (Paphy) has been studied in vitro. Ferritin prepared by classical procedures involving thermal denaturation releases its iron less effectively than ferritin isolated by a modified procedure that avoids this step. Desferrioxamine B and rhodotorulic acid are the most effective in releasing iron from both preparations of ferritin. When FMN is added, iron release by desferrioxamine B, rhodotorulic acid, and 2,3-dihydroxybenzoate was effectively blocked, whereas both bipyridyl and Paphy showed a marked simulation. A substantial increase in iron release was also observed for bipyridyl and Paphy with ascorbate; a less important increase was noted for rhodotorulic acid. EDTA exerted a marked inhibition of iron release from ferritin with rhodotorulic acid, 2,3-dihydroxybenzoate, bipyridyl, and Paphy. The effects of citrate and oxalate on iron release by the chelators was small. The effect of the concentration of flavin on iron release from ferritin by bipyridyl and desferrioxamine B have been studied. Desferrioxamine is unable to mobilize FeII from ferritin following reduction by reduced FMN, whereas bipyridyl can rapidly complex the ferrous iron. The results are discussed in the context of our current concepts of storage iron mobilization in the treatment of iron overload. 相似文献
10.
Conrauanalactone has been isolated from the bark of Garcinia conrauana Engl. (Guttiferae) and identified, on the basis of spectral and chemical evidence, as 4-hydroxy-6-pentadecyl- 2-pyrone. Minor constituents of the bark have been identified as 5,7-dihydroxychromone and eriodictyol. 相似文献