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741.
742.
Our study was designed to examine how components of complex mixtures can
inhibit the binding of other components to receptor sites in the olfactory
system of the spiny lobster Panulirus argus. Biochemical binding assays
were used to study how two- to six-component mixtures inhibit binding of
the radiolabeled odorants taurine, L-glutamate and
adenosine-5'-monophosphate to a tissue fraction rich in dendritic membrane
of olfactory receptor neurons. Our results indicate that binding inhibition
by mixtures can be large and is dependent on the nature of the odorant
ligand and on the concentration and composition of the mixture. The binding
inhibition by mixtures of structurally related components was generally
predicted using a competitive binding model and binding inhibition data for
the individual components. This was not the case for binding inhibition by
most mixtures of structurally unrelated odorants. The binding inhibition
for these mixtures was generally smaller than that for one or more of their
components, indicating that complex binding interactions between components
can reduce their ability to inhibit binding. The magnitude of binding
inhibition was influenced more by the mixture's precise composition than by
the number of components in it, since mixtures with few components were
sometimes more inhibitory than mixtures with more components. These
findings raise the possibility that complex binding interactions between
components of a mixture and their receptors may shape the output of
olfactory receptor neurons to complex mixtures.
相似文献
743.
An experimental method to selectively label side-chain NH2 groups of glutamine and asparagine in proteins with 15N is proposed. This selective labeling method enables to observe only 15NH2 resonances and thus, to discriminate between 15NH and 15NH2 resonances in a 1H-detected heteronuclear correlation spectrum. This method gives results with approximately two times higher sensitivity than those obtained by elaborate pulse sequences such as DEPT-HSQC and will be useful for studying the molecular interaction involving the side chains of Asn and Gln residues. 相似文献
744.
Jeanie McMillin-Wood Paul E. Wolkowicz Alice Chu Charlotte A. Tate Margaret A. Goldstein Mark L. Entman 《BBA》1980,591(2):251-265
Ca2+ transport and respiratory characteristics of two preparations of cardiac mitochondria (Palmer, J.W., Tandler, B. and Hoppel, C.L. (1977) J. Biol. Chem. 252, 8731–8739) isolated using polytron homogenization (subsarcolemmal mitochondria) and limited Nagarse exposure (intermyofibrillar mitochondria) are described.The Nagarse procedure yields mitochondria with 50% higher rates of oxidative phosphorylation than the polytron-prepared mitochondria in both rat and dog. Rat hear intermyofibrillar mitochondria contain 50% more cytochrome aa3 than the polytron preparation, whereas in the dog, cytochrome aa3 content is not significantly different. Cytochrome oxidase activities and cytochrome c, c1 and b contents were comparable in both populations of rat and dog heart mitochondria.The V of succinate-supported Ca2+ accumulation for Nagarse-prepared mitochondria from rat heart was 1.8-fold higher than the polytron-prepared mitochondria. In dog heart, the Nagarse preparation showed a 3.0-fold higher V for Ca2+ uptake compared to the polytron preparation. A lower apparent affinity for Ca2+ was demonstrated in the intermyofibrillar mitochondria for both species (Km is 2–2.5-fold higher). The Hill coefficient was 1 both mitochondrial types. Subsarcolemmal mitochondria from both species were treated with Nagarse to determine the role of this treatment on the observed differences. Nagarse did not alter any kinetic parameter of Ca2+ uptake.The properties of these mitochondria with reference to their presumed intracellular location may pertain to the role of mitochondria as an intracellular Ca2+ buffering mechanism in contractile tissue. 相似文献
745.
H Kitagawa M Takaoka H Nakada S Fukui I Funakoshi T Kawasaki S Tate F Inagaki I Yamashina 《Journal of biochemistry》1991,110(4):598-604
We have determined the structures of six oligosaccharides isolated from human milk using a monoclonal antibody, MSW 113. The isolation involved affinity chromatography on a column of the immobilized monoclonal antibody and high-performance liquid chromatography. From the results of 500 and 600 mHz 1H NMR spectroscopy and fast atom bombardment-mass spectrometry their structures were deduced to be: [formula; see text] Two of these oligosaccharides, numbers 4 and 5, have not previously been described. All of them bound to MSW 113, but their reactivities are weaker than those of sialyl-Le(a) oligosaccharides. The results indicate that MSW 113 reacts with oligosaccharides with the mono- and disialyl-Le(a), and other sialyl type 1 structures. 相似文献
746.
747.
Yoshito Fujimoto Takuma Shiraki Yuji Horiuchi Tsuyoshi Waku Akira Shigenaga Akira Otaka Tsuyoshi Ikura Kazuhiko Igarashi Saburo Aimoto Shin-ichi Tate Kosuke Morikawa 《The Journal of biological chemistry》2010,285(5):3126-3132
The important roles of a nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) are widely accepted in various biological processes as well as metabolic diseases. Despite the worldwide quest for pharmaceutical manipulation of PPARγ activity through the ligand-binding domain, very little information about the activation mechanism of the N-terminal activation function-1 (AF-1) domain. Here, we demonstrate the molecular and structural basis of the phosphorylation-dependent regulation of PPARγ activity by a peptidyl-prolyl isomerase, Pin1. Pin1 interacts with the phosphorylated AF-1 domain, thereby inhibiting the polyubiquitination of PPARγ. The interaction and inhibition are dependent upon the WW domain of Pin1 but are independent of peptidyl-prolyl cis/trans-isomerase activity. Gene knockdown experiments revealed that Pin1 inhibits the PPARγ-dependent gene expression in THP-1 macrophage-like cells. Thus, our results suggest that Pin1 regulates macrophage function through the direct binding to the phosphorylated AF-1 domain of PPARγ. 相似文献
748.
749.
750.
The Escherichia coli ribosomal protein L11 suppresses release factor 2 but promotes the release factor 1 activities in peptide chain termination 总被引:8,自引:0,他引:8
The incubation of the 50 S ribosomal subunits of Escherichia coli with 1.5 M LiCl yields 1.5c core particles depleted in 14 proteins and inactive in peptide chain termination. In codon-dependent peptidyl-tRNA hydrolysis the release factor 1 (RF-1)-induced reaction essentially depends on both L11 and L16 whereas the release factor 2 (RF-2)-induced reaction is depressed by L11 and stimulated by L16. Omission of L11 results in a several-fold increase in the specific activity of the RF-2. Functional complexes are formed with RF-2 at an apparent Km (dissociation constant) for the termination codon 5-fold lower than with reconstituted ribosomes containing L11; the Vmax for the hydrolysis is unchanged. L11 suppresses this effect when added to the core at close to molar equivalence. In contrast, RF-1 has a very low activity if ribosomes lack L11 and this can be restored by titration of L11 back to the core. This is the first example of a differential or an opposite effect of a ribosomal component on the activities of the two release factors, and the studies suggest that L11 has a critical role in the binding domain for the two factors. 相似文献