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11.
F Ramirez S I Tu P R Chatterji B McKeever J F Marecek 《Archives of biochemistry and biophysics》1984,230(1):61-68
The reaction of fluorescamine with ammonia, benzylamine, o,p-dimethylbenzylamine, 2-phenylethylamine, p-aminobenzoic acid, and the mycosamine-containing macrolide antibiotic, amphotericin B, yield compounds which induce significant effects on mitochondrial activities. From their effects on energy-yielding processes which lead to transmembranous proton movements, the compounds may be divided into three classes. While all modifiers significantly inhibit proton movement induced by both ATP hydrolysis and electron transfer in mitochondria, their influence on the primary energy yielding steps are quite different. Class I modifiers, e.g., the compound made from amphotericin B, inhibit electron transfer but have no effect on the Pi release associated with ATP hydrolysis. Class II modifiers, e.g., the compound made from benzylamine, inhibit respiration but stimulate Pi release. Class III modifiers, e.g., the compound made from p-aminobenzoic acid, on the other hand, only slightly increase Pi release but have no effect on redox reactions. These and other effects of the modifiers are taken to mean that the proton movements and their associated energy-yielding processes are only linked indirectly. The effects of the modifiers on State 3 mitochondrial activities were also investigated. Although all the modifiers decrease the rates of both State 3 respiration and its coupled ATP synthesis, the efficiency of energy conversion measured by the P/O ratio remains unaltered. 相似文献
12.
The secondary structure of the major neurotoxin from the sea snake Lapemis hardwickii was investigated by several methods of conformational analysis: structure prediction, circular dichroism, and laser Raman spectroscopy. From the primary structure, secondary structure prediction yielded two regions of β-sheet structure at residues 1–7 and 41–45. β-Turns were predicted at residues 14–17, 20–23, 30–33, 37–40, and 46–49. From the predictions, the toxin appears to be composed of approximately 20% β-sheet and 33% β-turn. The CD spectrum of the native toxin appears to be a hybrid of model spectra for β-sheet and β-turn proteins. The pH perturbation studies on the toxin observed by CD demonstrated that the toxin is a very stable molecule except at extremely high or low pH values. The Raman data indicated that the toxin contains both antiparallel β-sheet and β-turn structure. Using two methods of secondary structure quantitation from Raman spectra the molecule was calculated to contain 35% β-sheet from one method and 27% from the other. Overall, the various methods demonstrate that the toxin is composed of β-sheet and β-turn structure with little or no α-helix present. From the comparison of these different techniques appreciation can be gained for the necessity of several methods when identifying and quantitating secondary structure. 相似文献
13.
Relaxed circular SV40 DNA as cleavage intermediate of two restriction endonucleases. 总被引:7,自引:4,他引:3 下载免费PDF全文
We have determined the mode of cleavage of superhelical SV40 DNA (Form I) by restriction endonucleases EcoRI and HpaII at 37 degrees C. By analysis with agarose gel electrophoresis and direct examination with dark field electron microscopy, we found that a large amount of the single-nicked circular DNA (Form II) was produced before the linear SV40 DNA (Form III) appeared. Thus, both restriction enzymes cleave only one strand of the superhelical DNA first. The second cleavage on the complementary strand occurred after a lag period. The first order rate constant for the second cleavage by EcoRI endonuclease was determined and a kinetic reaction scheme for both enzymes is proposed. 相似文献
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The interaction of myotoxin alpha with intact sarcoplasmic reticulum (SR) components was investigated, and two SR proteins were identified that associated with myotoxin a. One of the proteins has an apparent molecular weight similar to the Ca(2+)-ATPase, the major SR protein responsible for calcium loading. Ca(2+)-ATPase was purified, and its interaction with myotoxin a was studied. Evidence for specific binding of myotoxin a to Ca(2+)-ATPase was established by isolating chemically cross-linked myotoxin a-Ca(2+)-ATPase complexes and further proving their association with anti-myotoxin a antibodies. The binding region of myotoxin a was further delineated by cleaving the protein with cyanogen bromide (CNBr) into two fragments, a larger N-terminal fragment of 28 residues and a smaller C-terminal fragment of 14 residues. Competition experiments with 125I-myotoxin a showed that the C-terminal fragment competed better against 125I-myotoxin a than the N-terminal fragment for SR protein binding. Two overlapping peptides covering the sequence of the N-terminal fragment were synthesized to clarify the interaction of the N-terminal fragment of myotoxin a with SR proteins. A 16-residue peptide corresponding to residues 1-16 competed strongly with 125I-myotoxin a, while a second peptide (residues 13-28) did not. 相似文献
16.
Taxonomic relations between archaebacteria including 6 novel genera examined by cross hybridization of DNAs and 16S rRNAs 总被引:9,自引:0,他引:9
Jenn Tu David Prangishvilli Harald Huber Gertrud Wildgruber Wolfram Zillig K. O. Stetter 《Journal of molecular evolution》1982,18(2):109-114
DNAs from 16 species of archaebacteria including 6 novel isolates were hybridized with 16S rRNAs from 7 species representing different orders or groups of the urkingdom of archaebacteria. The yields, normalized for the number of genes per microgram of DNA, and the temperature stabilities of all hybrids were determined and related to each other. A taxonomic tree constructed from such fractional stability data reveals the same major divisions as that derived from comparative cataloging of 16S rRNA sequences. The extreme halophiles appear however as a distinct order besides the three known divisions of methanogens. The methanogens, the halophiles and Thermoplasma form one of two clearly recognizable branches of the archaebacterial urkingdom. The order represented by Sulfolobus and the related novel order Thermoproteales form the other branch. Three novel genera, Thermoproteus, Desulfurococcus and the "stiff filaments" represent three families of this order. The extremely thermophilic methanogen Methanothermus fervidus belongs to the Methanobacteriales. SN1, a methanogen from Italy, appears as another species of the genus Methanococcus. Another novel methanogen, M3, represents a genus or family of the order Methanomicrobiales. 相似文献
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A major toxin was isolated from the venom of the sea snake Pelamis platurus (yellow-bellied sea snake) by Sephadex G-50 and carboxymethylcellulose column chromatography. The LD50 of the pure toxin (Pelamis toxin a) was 0.044 mug/g in mice representing a tenfold increase in toxicity after purification. The toxin was homogeneous in acrylamide disc gel electrophoresis and eluted as a single peak after isoelectric focusing in a sucrose density gradient column. The isoelectric point was 9.69; thus it is a highly basic protein. The toxin contained 55 amino acid residues with four disulfide linkages. When all disulfide linkages were reduced and alkylated, the toxic action of the pure toxin disappeared leading to the conclusion that the disulfide bonds of the neurotoxin were essential for toxic action. 相似文献
20.
Yung-Tsi Bolon Bindu Joseph Steven B Cannon Michelle A Graham Brian W Diers Andrew D Farmer Gregory D May Gary J Muehlbauer James E Specht Zheng Jin Tu Nathan Weeks Wayne W Xu Randy C Shoemaker Carroll P Vance 《BMC plant biology》2010,10(1):1-24