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E J Olender T Furukawa D J Woods D Fromm 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1987,185(4):377-384
The effects of histamine and several H1 and H2 receptor agents on Na+/H+ and Cl-/HCO-3 exchange systems of isolated gastric mucosal surface cells were studied. The cells were acid-loaded by the NH4Cl prepulse technique and the spontaneous Na+- and HCO-3-induced dissipation of the intracellular proton gradient (pHi) was followed using the metachromatic dye acridine orange. Histamine (10(-2-5) M) stimulates HCO-3-induced dissipation of the pHi but has no effect on Na+-induced or spontaneous dissipation. The H1 agonist 2-(2-aminoethyl)pyridine and the H2 agonist dimaprit also have no effect on Na+-induced or spontaneous pHi dissipation. However, both of these agents mimic the effect of histamine on HCO-3-induced dissipation, but only at a higher concentration (10(-3) M). The combination of 2-(2-aminoethyl)pyridine and dimaprit produces a histamine-like effect at lower concentrations (10(-5) and 10(-4) M). The effects of histamine are blocked by either the H1 antagonists diphenhydramine and pyrilamine or the H2 antagonists cimetidine and SKF 93479. The results suggest that the effect of histamine on HCO-3-induced dissipation of a pHi in gastric mucosal surface cells is mediated through a coordinated mechanism involving both H1 and H2 receptor sites. 相似文献
3.
The chloroplast genes coding for the 16S ribosomal RNA from several spectinomycin-resistant Nicotiana mutants were analyzed. Two classes of mutants were identified. In one class, a G to A base transition is found at position 1140 of the tobacco-chloroplast 16S rRNA gene, which eliminates an AatII restriction endonuclease site. This base transition is proximal to a mutation previously described for spectinomycin resistance in Escherichia coli. In the other class, a novel G to A transition is found at position 1012 of the 16S rRNA gene. Although the mutations in the two classes are 128 nucleotides apart, the secondary structure model for 16S rRNA suggests that the two mutated nucleotides are in spatial proximity on opposite sides of a conserved stem structure in the 3' region of the molecule. Phylogenetic evidence is presented linking this conserved stem with spectinomycin resistance in chloroplasts. Perturbation of the stem is proposed to be the molecular-genetic basis for rRNA-dependent spectinomycin resistance. 相似文献
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Shmuel Galili Hillel Fromm Dvora Aviv Marvin Edelman Esra Galun 《Molecular & general genetics : MGG》1989,218(2):289-292
Summary A streptomycin resistant Nicotiana plastome mutant, X/str
R6, was subjected to molecular analysis. In this mutant, a single nucleotide transition, C » T, in the chloroplast gene for ribosomal protein S12 alters codon 90 from proline to serine while the nucleotide sequence of the chloroplast 16 S rRNA gene is identical to that of the wild type. Mutant X/str
R6 thus differs from several previously reported streptomycin resistant chloroplast mutants which are altered in the gene for 16 S rRNA. 相似文献
6.
The site of substrate and fructose 2,6-bisphosphate binding to rabbit liver fructose-1,6-bisphosphatase 总被引:1,自引:0,他引:1
The binding site(s) in rabbit liver fructose-1,6-bisphosphatase for the active site binding ligand, fructose 6-phosphate, and the inhibitor, fructose 2,6-bisphosphate, have been investigated by using nuclear magnetic resonance spectroscopy. The distance from a nitroxide spin label to the bound ligands and the distance from the structural metal site to the bound ligands are about the same within experimental error. These data indicate that the two ligands probably bind at the active site in the rabbit liver enzyme. 相似文献
7.
Radiolabelled calmodulin has previously been used to screen cDNA expression libraries to isolate calmodulin-binding proteins.
We have modified this technique for the isolation of plant calmodulin-binding proteins. [35S]-methionine was used instead of the inorganic [35S]-sulfate, or125I used in previous methods. In addition, theE. coli pET expression system was chosen to obtain high levels of recombinant calmodulin at the time of labelling. The procedure
thus takes into account both the specific activity of the probe and the amount of protein necessary for screening a large
number of filters. Here we describe in detail a procedure for the production and purification of [35S]-recombinant calmodulin and the use of the radiolabelled protein as a probe to screen plant cDNA expression libraries. The
[35S]-labeled calmodulin probe easily detects the λICM-1 phage encoding a partial mouse calmodulin-dependent protein kinase II
that was previously isolated using a [125I]-calmodulin probe (Sikela and Hahn, 1987). Subsequently, a tobacco root cDNA expression library was screened and a positive
clone encoding a calcium-dependent calmodulin-binding protein was isolated. 相似文献
8.
1H and 31P nuclear magnetic resonance was used to investigate the interaction of AMP and fructose 2,6-bisphosphate (Fru-2,6-P2) with bovine liver fructose-1,6-bisphosphatase. Mn2+ bound to fructose-1,6-bisphosphatase was used as a paramagnetic probe to map the active and AMP allosteric sites of fructose-1,6-bisphosphatase. Distances between enzyme-bound Mn2+ and the phosphorus atoms at C-6 of fructose-6-P and alpha-methyl-D-fructofuranoside 1,6-bisphosphate were identical, and the enzyme-Mn to phosphorus distance determined for the C-6 phosphorus atom of Fru-2,6-P2 was very similar to these values. Likewise, the enzyme-Mn to phosphorus distances for Pi, the C-1 phosphorus atom of alpha-methyl-D-fructofuranoside 1,6-bisphosphate, and the C-2 phosphorus atom of Fru-2,6-P2 agreed within 0.5 A. The distance between enzyme-bound Mn2+ and the phosphorus atom of AMP was significantly shorter than the distances obtained for any of the aforementioned ligands, but the presence of Fru-2,6-P2 caused the enzyme-Mn to phosphorus distance for AMP to lengthen markedly. NMR line broadening of AMP protons was studied at various temperatures. The dissociation rate constant was found to be greater than 20 s-1. It was concluded that Fru-2,6-P2 strongly affects the interaction of AMP with fructose-1,6-bisphosphatase and that the sugar most likely acts at the active site of the enzyme. 相似文献
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