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21.
Summary Hepatic-FABP was labelled at cysteine-69 with the fluorescent environmentally sensitive reporter group AEDANS. The labelled protein had an emission maximum at 465 nm indicating that cysteine-69 was buried in a non-polar environment. The modified protein was still able to bind ligands such as oleic acid, oleoyl CoA and haem. The affinity of AEDANS-FABP for haem was unaltered as compared with the native protein indicating that cysteine-69 must be remote from the ligand binding site. The binding of oleic acid did not significantly perturb the fluorescence emission spectrum of the fluorescent reporter group suggesting that there are not large conformational changes in the region of cysteine-69 on fatty acid binding. The binding of stoichiometric amounts of oleoyl CoA was accompanied by a small fluorescence enhancement which suggests that fatty acyl CoAs may interact with other regions of the FABP molecule not involved in fatty acid binding.Abbreviations FABP
Fatty Acid-Binding Protein
- AEDANS
5-[2-(Acetyl)aminoEthyl]Aminonaphthalene-1-Sulphonic Acid
- AAEDANS
5-[2-(Iodoacetyl-AminolEthyl] aminonaphthalene-1-Sulphonic Acid
- DTNB
5,5Dithiobis-(2-Nitrobenzoic acid) 相似文献
22.
The monofunctional thiol reagents N-ethylmaleimide (NEM) and methyl methanethiosulfonate (MMTS) stimulate ouabain resistant (OR) electroneutral K:Cl cotransport in LK sheep red blood cells at low, but not at high concentrations. Diamide (DM), on the other hand, only stimulates OR K:Cl flux (Lauf, P.K., J. Memb. Biol. 101: 179–188, 1988). The DM stimulated K:Cl cotransport was decreased toward the control value prior to DM stimulation when NEM or MMTS were added, subsequently. The inhibitory effect was dependent on the compound's concentration and exposure time and, in the case of MMTS, was reversed upon addition of dithiothreitol (DTT). The inhibition was more prominent when NEM treatment was performed at pH 8.0 and disappeared at pH 6.0. In contrast the NEM stimulatory effect was most effective when the pH of NEM treatment was 6.0 (Bauer, J. & Lauf, P.K., J. Memb. Biol. 73: 257–261, 1983). The results suggest the existence of additional, however, inhibitory thiol groups in the already thiol-activated K:Cl cotransporter, with a different pKa value and a lower affinity for NEM or MMTS as compared to the stimulatory thiol groups. Like the activating thiols, the inhibitory sulfhydryls appeared to be inaccessible to non-penetrating thiol reagents and hence, must be located deeper within the red cell membrane. 相似文献
23.
Garry J. Smith Heinz W. Kunz Harold A. Dunsford Thomas J. Gill III 《Cell biology and toxicology》1990,6(2):205-217
The histopathological response and cell culture characteristics of liver cells from the R16 (grc
–) strain of rats, which carries an MHC-linked deletion, were examined one week after a single intraperitoneal injection of 200 mg/ kg body weight diethylnitrosamine (DEN) and were compared with the response of liver cells from wild type (grc+) rats. The DEN exposure induced hydropicl vacuolar changes in the parenchymal cells and a limited proliferation of oval cells in the periportal areas of the livers of both grc+ and grc rats. Primary culture of collagenase-digested livers consisted of parenchymal, bile ductular and oval-related cells as determined by cell-specific immunohistochemistry. Subpassaged cells from grc+ rats exhibited oval cell ultrastructural morphology, inducible histochemical staining for gammaglutamyl transpeptidase (GGT), and DEN-associated onset of anchorage-independent growth. Primary cultures of liver cells from R16 rats consistently failed to form cell strains upon subpassage.Abbreviations DEN
diethylnitrosamine
-
grc
growth and reproduction complex
- GGT
gamma-glutamyl transpeptidase
- MHC
major histocompatibility complex 相似文献
24.
Jui H. Wang 《Journal of bioenergetics and biomembranes》1988,20(4):407-422
Recent studies of chemically modified F1-ATPases have provided new information that requires a revision of our thinking on their catalytic mechanism. One of the subunits in F1-ATPase is distinguishable from the other two both structurally and functionally. The catalytic site and regulatory site of the same subunit are probably sufficiently close to each other, and the interaction between the various catalytic and regulatory sites are probably sufficiently strong to raise the uni-site rate of ATP hydrolysis by several orders of magnitude to that of promoted (multi-site) ATP hydrolysis. Although all three subunits in F1 possess weak uni-site ATPase activity, only one of them () catalyzes promoted ATP hydrolysis. But all three subunits catalyze ATP synthesis driven by the proton flux. Internal rotation of the 33 or 3 moiety relative to the remainder of the F0F1 complex did not occur during oxidative phosphorylation by reconstituted submitochondrial particles. 相似文献
25.
The stem-galling sawfly Euura lasiolepisuses one or more plant wound compounds resulting from oviposition scars as cues in host discrimination (avoiding sites occupied by conspecifics). Four experiments were conducted to test hypotheses about how Euurapartitions resources. Experiment 1 demonstrated that Euuraavoids ovipositing on nodes with scars from previous ovipositions. Experiment 2 showed no evidence that the sawfly uses oviposition-deterring pheromones and indicated there is a time lag following oviposition before the oviposition scar becomes a deterrent. Experiment 3 showed that sawflies avoid artificially formed scars, demonstrating that a plant cue alone can lead to host discrimination. Experiment 4 showed that visual or tactile cues are not necessary for host discrimination and indicated that a plant wound compound functions as an oviposition deterrent. Both experimental results and field surveys showed that Euuraoviposition scars were more uniformly distributed than expected if sawflies were ignoring previous ovipositions. 相似文献
26.
在pH7.5条件下,用NBS对PEP羧化酶中色氨酸残基进行共价修饰表明,PEP羧化酶中48个色氨酸残基均能被NBS修饰。用邹承鲁图解法求得,其中4个残基为酶表现催化活性所必需的。 PEP羧化酶的变构效应剂G6P、Gly及Mal分别与酶预保温后,再经NBS修饰,前两种处理中,同样浓度的NBS所用修饰的色氨酸残基数和处理后的残存酶活与对照相比有很大的差异,而用Mal处理的,两者与对照相差无几。 相似文献
27.
Floral scents of male and female inflorescences of three dioeciousSalix species were collected by head-space adsorption, and analysed by GC-MS. InSalix caprea andS. cinerea 1,4-dimethoxy benzene was the main compound, and male and female scents showed a high degree of resemblance. No dominant compound was found inS. repens and malefemale scent similarity was low. Floral scent inSalix is likely a strong orientation cue, guiding pollinators between male and female plants ensuring pollen transfer and pollination. We suggest that a high degree of male-female floral scent resemblance is coupled to a high degree of insect pollination. Floral scent does not promote reproductive isolation betweenS. caprea andS. cinerea. 相似文献
28.
两种品系油菜植株成分与蚜虫种群消长及成蚜翅型的关系 总被引:2,自引:0,他引:2
本文研究两种品系油菜植株成分与桃蚜(Myzus persicae(Sulzer))、萝卜蚜(Lipaphis erysimi(Kaltenbach))的种群消长及成蚜翅型的关系.经分析得出如下结果:1.桃蚜种群消长与苏氨酸、赖氨酸、组氨酸、丙氨酸、硬脂酸等含量有关;桃蚜成蚜无翅率与精氨酸、谷氨酸、酪氨酸、异亮氨酸等含量有关.2.萝卜蚜种群消长与苏氨酸、蛋氨酸、异亮氨酸、苯丙氨酸、酪氨酸、含水量有关;萝卜蚜成蚜无翅率与含水量.亚麻酸.苏氨酸、油酸,天门冬氨酸、丝氯酸、亚油酸等含量有关. 相似文献
29.
SHOKO YASUKAWA HIDETOSHI KATO RYOHEI YAMAOKA HAJIME TANAKA HIROHITO ARAI SHOICHI KAWANO 《Plant Species Biology》1992,7(2-3):121-140
Abstract Volatile substances emitted from the flowers of eight Magnolia taxa ( M. sieboldii ssp. japonica, M. praecocissima var. praecocissima and var. borealis, M. tomentosa, M. salicifolia, M. obovata, M. denudata, and M. grandiflora ) and one Michelia species ( M. compressa ) (Magnoliaceae) were examined and identified using GC-MS. Volatile substances of these Magnolia and Michelia species consist primarily of monoterpenoids and sesquiterpenoids produced by the mevalonate pathway, acetogenins by the acetate-malonate pathway, and phenyl-propanoids by the shikimate pathway. These Magnolia and Michelia species all possessed various combinations of volatile monoterpenoids, acetogenins, and phenylpropanoids, except for Magnolia obovata , which emitted primarily sesquiterpenoids. Free amino acids in pollen of 12 Magnolia and one Liriodendron species were also analyzed, and their value as food sources for pollinators evaluated.
Pollinators visiting the flowers of five Magnolia species were collected in their native sites and identified. Their behaviors and roles as pollinating agents were assessed. 相似文献
Pollinators visiting the flowers of five Magnolia species were collected in their native sites and identified. Their behaviors and roles as pollinating agents were assessed. 相似文献
30.