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Wendell L. Combest Timothy J. Bloom Lawrence I. Gilbert 《Journal of neurochemistry》1988,51(5):1581-1591
The effects of the naturally occurring polyamines spermine and spermidine on phosphorylation promoted by cyclic AMP (cAMP)-dependent protein kinase (PK) (cAMP-PK; EC 2.7.1.37) were studied using the brain of the tobacco hornworm, Manduca sexta. Four particulate-associated peptides (280, 34, 21, and 19 kilodaltons) in day 1 pupal brains are endogenous substrates for a particulate type II cAMP-PK. These phosphoproteins are present in brain synaptosomal, as well as microsomal, particulate fractions but are not present in the cytosol. They are distributed throughout the CNS and PNS and are present in several nonneuronal tissues as well. Phosphorylation of these proteins via cAMP-PK was inhibited markedly by micromolar concentrations of spermine and spermidine. Other particulate-associated peptides phosphorylated via a Ca2+/calmodulin-PK or Ca2+ and cAMP-independent PKs were unaffected by polyamines, whereas the phosphorylation of a 260-kilodalton peptide was markedly enhanced. Spermine did not exert its inhibitory effect indirectly by enhancement of cAMP or ATP hydrolysis or via proteolysis, but its action appears to involve a substrate-directed inhibition of cAMP-PK-promoted phosphorylation as well as enhanced dephosphorylation. Although addition of spermine resulted in marked ribosome aggregation in synaptosomal and microsomal particulate fractions, this phenomenon was not involved in the inhibition of cAMP-PK-promoted phosphorylation. 相似文献
4.
We studied the effects of various polyamines on bud regeneration in thin-layer tissue explants of vegetative and floweringNicotiana tabacum L. cv. Wisconsin 38, in which application of exogenous spermidine (Spd) to vegetative cultures causes the initiation and
development of some flower buds (Kaur-Sawhney et al. 1988 Planta173, 282). We now show that this effect is dependent on the time and duration of application, Spd being required from the start
of the cultures for about three weeks. Neither putrescine nor spermine is effective in the concentration range tested. Spermidine
cannot replace kinetin (N6-furfurylaminopurine) in cultures at the time of floral bud formation, but once the buds are initiated in the presence of
kinetin, addition of Spd to the medium greatly increases the number of floral buds that develop into normal flowers. Addition
of Spd to similar cultures derived from young, non-flowering plants did not cause the appearance of floral buds but rather
induced a profusion of vegetative buds. These results indicate a morphogenetic role of Spd in bud differentiation.
Dedicated to Professor Hans Mohr on the occasion of his 60th birthday 相似文献
5.
Abstract: The NMDA receptor exhibits increased sensitivity to stimulation during early development compared with the adult. In this study, we examined modulation of the NMDA receptor by polyamines during development to see if it correlates with differences in the functional responsiveness of the NMDA receptor. [3H]MK-801 binding was measured in discrete brain regions in the presence and absence of polyamines in 3-, 7-, 15-, 25-, and 60-day-old Sprague-Dawley rats. [3H]MK-801 binding increased between postnatal days 3 and 15, with adult levels of binding being reached between days 15 and 25. Spermidine (75 μM) caused maximal stimulation of [3H]MK-801 binding during early development, ranging from 250% in the thalamus to 450% in the caudate putamen at postnatal day 3. This effect gradually declined to levels seen in the adult by postnatal days 15–25. During all developmental stages, the stimulation seen was greater in the caudate putamen compared with the hippocampus. Diethylenetriamine (1 μM) exhibited similar developmental and regional heterogeneity in its effects on [3H]MK-801 binding, producing substantial stimulation of binding in the neonate, but not in the adult. The EC50 and Emax values for the stimulatory effect of spermidine were significantly higher at day 7 compared with the adult. Unlike spermidine and diethylenetriamine, there was no regional variation in the effects of the putative “polyamine site” inverse agonist 1,10-diaminodecane at any age and only a slightly attenuated inhibition at postnatal day 3 compared with the adult. This lack of complementarity in the regional and developmental profiles of spermidine and diethylenetriamine, on the one hand, and 1,10-diaminodecane, on the other, suggests that their effects on [3H]MK-801 binding are mediated at different sites. The altered sensitivity of the NMDA receptor to polyamines during development could reflect the expression of molecular variants with different sensitivities to modulation by polyamines. 相似文献
6.
Summary The kinetics of putrescine and spermidine uptake and the influence of calcium on the kinetic parameters of the transport process were investigated in protoplasts isolated from carrot phloem parenchyma. Spermidine uptake dependence on external concentration was biphasic, both in the absence and in the presence of 1 mM CaCl2. In the first case, saturation was reached at 0.1 to 0.25 mM and the Km value was 43µM. When calcium was added, the Km and Vmax increased. A similar pattern was found with regard to putrescine uptake. Moreover, in order to clarify the mode of action of calcium on polyamine uptake, lanthanides (lanthanum and gadolinium) were utilised as Ca+2-channel antagonists. When protoplasts were preincubated with these lanthanides, the stimulatory effect exerted by Ca+2 on polyamine uptake was almost totally abolished. On the other hand, if lanthanum was supplied instead of calcium, it gave rise to a small enhancement of polyamine transport. These results induce us to suggest that calcium acts on polyamine uptake both by binding to external sites on the plasmalemma and by penetrating into the cell. 相似文献
7.
Thorsten Wöhl Hannelore Klier Hubert Ammer Friedrich Lottspeich Viktor Magdolen 《Molecular & general genetics : MGG》1993,241(3-4):305-311
In Saccharomyces cerevisiae, hypusine-containing proteins are encoded by two closely related genes, HYP1 and HYP2, which are regulated reciprocally by oxygen and heme. We have purified the aerobically expressed hypusine-containing proteins from yeast. The three proteins detected (two isoforms, which differ in their pI values, and a degradation product thereof, lacking the N-terminal 10 amino acid residues) are all encoded by HYP2. The N-terminus of both isoforms is formed by acetylation of a serine residue after cleavage of the first methionine. Cells mutant for hyp2 are unable to grow aerobically. However, under anaerobic conditions these mutants display no obvious phenotype, presumably because the strictly anaerobically expressed HYPI gene product (Hyp1p) is present. This implies that Hyp1p and Hyp2p fulfill very similar functions. In fact, Hyp1p can substitute for Hyp2p under aerobic conditions, when expressed under the control of the GAL1 promoter in hyp2 mutant cells.Abbreviations
HYP1 and HYP2
S. cerevisiae genes encoding hypusine-containing protein Hyplp and Hyp2p, respectively 相似文献
8.
Changes in the NMR chemical shifts of protons adjacent to the nitrogen atoms of Spermidine which are undergoing protonation have been measured by two-dimensional heteronuclear coupled NMR. Data thus obtained measure the dependence of the state of protonation of individual nitrogens on the pH, and permit calculation of the microprotonation constants of Spermidine and the concentrations of all of the variously protonated Spermidine species present at any pH. 相似文献
9.
We have investigated the binding of 3-[125I]iododizocilpine ([125I]iodo-MK-801) to the N-methyl-D-aspartate (NMDA) receptor in well-washed rat brain membranes. [125I]Iododizocipline binding was displaced by the following: dizocilpine greater than thienylphencyclidine greater than phencyclidine greater than ketamine. Binding of [125I]iododizocilpine was enhanced by glutamate, glycine, and spermidine, whose actions could be reversed by CGS-19755, 7-chlorokynurenate, and arcaine, respectively. [125I]Iododizocilpine binding was also enhanced by a number of divalent cations, including Ba2+, Ca2+, Mg2+, Mn2+, and Sr2+, and several monovalent cations, including Na+ and K+. These cations enhanced [125I]iododizocilpine binding by an action at the polyamine site. In addition, the inhibitory effects associated with high concentrations of these cations was markedly reduced compared to those found in previous studies with [3H]dizocilpine. Analysis of the ability of spermidine, Mg2+, and Sr2+ to alter the inhibition of [125I]iododizocilpine by arcaine gave pA2 values of 5.41, 4.47, and 4.93, corresponding to EC50 concentrations of 3.9, 34.7, and 12.0 microM, respectively, suggesting that physiological concentrations of Mg2+ may occupy the polyamine site. These results demonstrate that [125I]iododizocilpine is a useful probe for the NMDA receptor. Moreover, its high specific activity and relative insensitivity to the inhibitory actions of divalent cations should make [125I]iododizocilpine a valuable ligand for the study of NMDA receptors in intact cellular systems. 相似文献
10.
Senescence of Petunia hybrida L. flowers is accompanied by a climacteric pattern in ethylene production and a rapid decline in the levels of putrescine and spermidine during the preclimacteric phase. The decrease in spermidine is caused by the decline in the availability of putrescine which is initially synthesized from L-arginine via agmatine and N-carbamoylputrescine. Inhibition of putrescine and polyamine synthesis resulted in a rapid drop in the levels of putrescine and spermidine without resulting in a concomitant increase in ethylene production. These results indicate that polyamine synthesis is not involved in the control of ethylene synthesis through its effect on the availability of S-adenosylmethionine, and is confirmed by the results obtained with pollinated flowers. Treatment with polyamines may stimulate or suppress ethylene production in the corolla, depending on the concentrations applied. In unpollinated flowers the onset of the climacteric rise in ethylene production was accelerated after treatment with polyamines. However, in pollinated flowers this process was delayed as a result of treatment with low concentrations of polyamines. The effects of exogenous polyamines on ethylene production in both pollinated and unpollinated flowers indicate that ethylene synthesis in these flowers is not regulated by a feedback control mechanism. Although polyamines do not play a key role in the control of ethylene production during the early stages of senescence through their effect on the availability of S-adenosylmethionine, it appears that they play an important role in some of the other processes involved in senescence.Abbreviations ACC
1-aminocyclopropane-1-carboxylic acid
- MGBG
methylglyoxal bis-(guanylhydrazone)
- SAM
S-adenosylmethionine 相似文献