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11.
C Chatelet J Gaillard Y Pétillot M Louwagie J Meyer 《Biochemical and biophysical research communications》1999,261(3):885-889
Overexpression in Escherichia coli of the fdx4 gene from Aquifex aeolicus has allowed isolation and characterization of the first hyperthermophilic [2Fe-2S](Scys)(4) protein, a homodimer of M = 2 x 12.4 kDa with one [2Fe-2S] cluster per subunit. This protein is undamaged by heating to 100 degrees C for at least three hours. The primary structure, in particular the characteristic distribution of the four cysteine ligands of the metal site, and the spectroscopic properties of the A. aeolicus protein relate it to well characterized [2Fe-2S] proteins from Clostridium pasteurianum and Azotobacter vinelandii. These proteins are also homologous to subunits or domains of hydrogenases and NADH-ubiquinone oxidoreductase (Complex I) of respiratory chains. The A. aeolicus [2Fe-2S] protein is thus representative of a presumably novel protein fold involved in a variety of functions in very diverse cellular backgrounds. 相似文献
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Immunoperoxidase labeling of fibronectin in one-day-old mouse first lower molars allowed to visualize a striking redistribution of this glycoprotein during terminal cytodifferentiation of odontoblasts. The modifications involved both extracellular and cell surface localizations. The possible roles of these modifications in terminal differentiation of odontoblasts are discussed. 相似文献
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The variety of results of crystallographic studies of the serine proteases complexed with isocoumarin inhibitors presents a challenging problem to modeling methods and molecular energetics. Therefore, the thermodynamic cycle-perturbation technique has been used to study a model system of elastase and two peptidic inhibitors. Using the program AMBER, the technique correctly predicts changes of the binding constants for the trifluoroacetyl dipeptide inhibitors in comparison with available experimental (kinetic and crystallographic) data. However, the absolute values obtained are shown to be sensitive to the specific electrostatic interaction potential parameters used in the simulations. The reader and user are cautioned that thermodynamic cycle-perturbation results may be too optimistic by underestimating the accuracy of free energy values. This is especially a matter of concern for those cases where a direct comparison with experimental values is not possible, viz., (1) the stimulation of binding of novel compounds, (2) structurally uncertain binding sites, or (3) structurally different binding modes. With our best 4-31G* ESP (electrostatic potential) charges we were able to reproduce experimentally determined free energy differences (delta delta A) with an accuracy of about 1.5 kcal/mol. Dynamically induced structural changes in the binding site of elastase, and particularly changes in hydrogen-bond patterns of the binding site, are also reported. 相似文献
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Summary Phage adsorption tests and transfection by electroporation were carried out to decide whether phage-resistance in Lactococcus lactis subsp. lactis strain 4513-5 is based on intracellular or extracellular mechanisms. Using high voltage (12.5 kV/cm) electroporation, untreated phage DNA was introduced into phage-sensitive and phage-resistant cells. Since phages showed low adsorption frequencies on resistant bacteria, resistance is localized in the cell wall preventing phage DNA from entering the cell. This is the only mechanism responsible for the resistance of L. lactis subsp. lactis 4513-5 against its homologous phage P4513-K12 and non-homologous phages P05M-13 and P05M-47, but not against phage P530-7 and phage P530-12. In the case of the latter two phage strains, intracellular resistance mechanisms are involved and discussed. 相似文献
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Summary Video-densitometric DNA measurements of Feulgenstained tissues of 42 day old eggs of the corn snake,Elaphe g. guttata (Columbridae, Serpentes), revealed a basic DNA content of 2C=2.17 pg, with somatic polyploidy in the allantois, the chorioallontois, the yolk sac, and other extraembryonic membranes. The maximum value determined was 128C (in binucleate cells 2×128C) at the distal pole of the egg. This is the first report of somatic polyploidy in a snake, and one of the first in reptiles in general. 相似文献