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21.
Ludwig M. G. Heilmeyer Jr. Jeung-Whan Han Rolf Thieleczek Magdolna Varsanyi Georg W. Mayr 《Molecular and cellular biochemistry》1990,99(2):111-116
Skeletal muscle triads are possessing the whole set of enzymes of the phosphatidylinositol (PI)-linked signal generating pathway, PI-kinase, PI(4)P-kinase, and PI(4,5)P2-phospholipase C (PLC). The activities of these enzymes are comparable to those found in other cell types for which a functional role of the PI-pathway in intracellular signal transduction has been established. For skeletal muscle an unequivocal function and an initiating signal for Ins(1,4,5)P3-liberation is still unknown. However, the observed Ca-dependency of PLC activity suggests that here Ins(1,4,5)P3 production is a consequence rather than a cause of increasing cytosolic Ca2+. Recently, the glycolytic enzyme aldolase, whose activity can be modulated by inositol polyphosphates, has been localized in the triadic structure. The enzyme which has a high affinity to Ins(1,4)P2, Ins(1,4,5)P3 and Ins(1,3,4,5)P4, seems to be compartmentalized to the junctional foot structure from which it is released upon binding of these molecules. This phenomenon could reflect a capability for regulation of the glycolytic flux even for aldolase, especially if a non steady-state situation in the junctional gap is considered. Meanwhile we have accumulated evidence for the operation of a partial glycolytic sequence in the junctional region established by the enzymes aldolase, glyceraldehyde-3-P (GAP) dehydrogenase and phosphoglycerate kinase. This system is able to produce ATP upon oxidation of GAP and could be, because of the inositol polyphosphate-sensing abilities of aldolase, a target for the membrane associated PI-pathway. The ATP production is however transient which indicates the coupling to an ATP hydrolyzing reaction. Thus, it appears that the ATP produced by the membrane associated system is effectively utilized by an ATP consuming membrane localized system like PI-metabolism or protein kinases. There are indications that exogeneously added ATP does not equilibrate with the ATP synthesized in the junctional region which suggests an effective structural or kinetical compartmentalization of this system. Therefore it is hypothesized that the ATP synthesized by the membrane associated glycolytic sequence is utilized in membrane localized reactions. 相似文献
22.
Hans Georg B?umert Akitsugu Kenmoku Gert Middelhoff Franz Ortanderl Alexander Thrun Heinz Faulstich Wolfgang Schiebler Hugo Fasold 《Journal of Protein Chemistry》1988,7(5):571-580
With the aid of tartryl-bis--aminocaprylazide artificial dimers were produced from F actin from rabbit striated muscle. These derivatives will not polymerize by themselves but are able to copolymerize fully with native G actin. By modification of a single side chain per dimer, this copolymerization was completely inhibited. The dimers are able to activate subfragment I ATPase of myosin and bind to DNase I with inactivation of the enzyme in the same manner as native G actin. Within the dimer, one ADP is immobilized and will exchange against ATP extremely slowly. The dimers do not bind to the mushroom toxin phalloidin. 相似文献
23.
Genetics of the quantitative Lp(a) lipoprotein trait 总被引:13,自引:1,他引:12
Gerd Utermann Hans Georg Kraft Hans Jürgen Menzel Thomas Hopferwieser Christoph Seitz 《Human genetics》1988,78(1):41-46
The Lp(a) lipoprotein is a complex particle composed of a low density lipoprotein (LDL)-like lipoprotein and the disulfide bonded Lp(a) glycoprotein. The complex represents a quantitative genetic trait. SDS gel electrophoresis under reducing conditions of sera followed by immunoblotting with affinity-purified polyclonal anti-Lp(a) demonstrated inter- and intra-individual size heterogeneity of the glycoprotein with apparent Mr in the range 400-700kDa. According to their relative mobilities compared to apo B-100 the Lp(a) patterns were categorized into phenotypes F, B, S1, S2, S3 und S4 and into the respective double-band phenotypes. This size heterogeneity seems to be controlled by multiple alleles designated LpF, LpB, LpS1, LpS2, LpS3, LpS4 and a null allele (LpO) at a single locus. Phenotype frequencies observed in 441 unrelated subjects were in good agreement with those expected from the genetic hypothesis. Comparison of Lp(a) lipoprotein concentrations in the different phenotypes revealed a highly significant association of phenotypes B, S1 and S2 with high, and phenotypes S3 und S4 with intermediate Lp(a) concentrations. A third mode is represented by the null phenotype were no Lp(a) band is detected upon immunoblotting and Lp(a) lipoprotein is low or absent. We conclude that the same gene locus is involved in determining Lp(a) glycoprotein phenotype and Lp(a) lipoprotein concentrations in plasma. This major gene seems to be the Lp(a) glycoprotein structural gene locus. 相似文献
24.
In the lichen genusUsnea different species ofTrebouxia-phycobionts as well as different haustorial types are known. The isolated and cultivated phycobiont ofUsnea longissima
Ach. was studied by light- and electron microscopy and resembles in cytomorphological details the type ofTrebouxia impressa
Ahmad. In addition to simple wall-to-wall contacts between the symbiotic components also intraparietal (=intrawall-)haustoria could be observed as the normal interaction type.
Frau Prof. Dr.Elisabeth Tschermak-Woess zu ihrem 70. Geburtstag gewidmet. 相似文献
25.
We isolated hybridomas that produced monoclonal antibodies specific for the UDP-galactose: sn -glycerol-3-phosphate α-D-galactosyltransferase (IFP synthase, EC 2.4.1.96), an enzyme involved in the volume regulation of Poterioochromonas malhamensis Peterfi. Western blotting of native gradient gels with the most reactive antibody S 162 revealed several immunoreactive proteins in crude homogenates suggesting the occurrence of multiple molecular mass species of the galactosyltransferase. The amount of the presumed enzyme monomer (64 kDa under native conditions) was strongly increased by a pH shift of crude homogenates from pH 8 to 6. During activation of the galactosyltransferase in the cell homogenate and also by shrinking the cells, the presumed enzyme monomer appeared to be proteolytically degraded generating stepwise products of 52 and 40 kDa. We assume that the proteolytically processed enzyme becomes highly active, but is very susceptible to further proteolytic degradation. 相似文献
26.
Electron Microscopic Studies of Spruce Needles in Connection with the Occurrence of Novel Forest Decline 总被引:3,自引:0,他引:3
Needles of four spruce trees showing different degrees of novel kinds of forest decline were investigated by electron microscopy. Green needles appearing at least superficially still intact were selected for the present investigation. Most of the mesophyll appeared to be undamaged. However, groups of atypical mesophyll cells were found close to the endodermis or the hypodermis. The chloroplasts of the apparently damaged cells were particularly affected. Changes in the matrix of the chloroplasts, i.e,. increased affinity to osmium, occurrence of extensive nests of plastoglobuli, as well as damage to the membranes, i.e. lesions in the envelope and abnormal thylakoid membranes, were observed. Signs of decomposition of other cellular structures including mitochondria were also detectable. There appeared to be a close correlation between the degree of damage at the whole tree level and the degree of damage occurring at the cellular level. It is concluded that particularly the lipids and the proteinsof, the membranes are affected by anthropogenic air pollutants and natural stressors. The altered membrane structure may for instance cause abnormal osmotic conditions for the cellular compartments and may impair transport processes and thus lead to lossof function not only of the cells but also of the whole needle. 相似文献
27.
Georg Miehe 《Plant Ecology》1988,79(1-2):21-32
The vegetation of Mt Everest is described by means of the dominant plant formations and characteristic features of biotopes. Climatic data givenin connection with weather observations show evidence that the extreme asymmetry of the altitudinal vegetation belt on the south and north slope is induced by heavy rainfall on the south slope and the desiccating effect of the Himalaya föhn in the valleys of the north slope. Biotope shift from hypsozonal distribution on the south slope to extrazonal distribution on the north slope is described, the patterns of the actual timber line are discussed in order to reconstruct the natural upper forest limit, and regressive plant successions during the last 400 years of man's impact are summarized. The dominant vegetation pattern of the alpine belt is compared with that in the European Alps. On the arid north slope alpine steppe communities occur up to 5 500 m. The highest altitudinal vegetation belt and the highest plant communities at 5 960 m are dominated by periglacial processes. The highest records of flowering plants (6 100/6 200 m) and lichens (7 400 m) are discussed in light of the present knowledge on high-altitude vegetation ecology. 相似文献
28.
Cell-free extracts from leaves of Rhus typhina L. (sumach) were found to transfer the 1-O-galloyl moiety of l,6-di-O-galloyl-β-d-glucose to the 2-position of the same compound, yielding 1,2,6-tri-O-galloyl-β-d-glucose and leaving 6-O-galloylglucose as the deacylated by-product. The enzyme catalyzing this ‘disproportionation’ was purified almost 1700-fold. It had a molecular weight of approx. 56 000, a K m value of 11.5 mM, was stable between pH 4.5 and 6.5, and most active at pH 5.9 and 40° C. The systematic name “1,6-di-O-galloyl-glucose: 1,6-di-O-galloylglucose 2-O-galloyltransferase” (EC 2.3.1.) was proposed for this new enzyme whose detection provided evidence that, in addition to β-glucogallin (1-O-galloyl-β-d-glucose), higher substituted glucose esters also have the potential to serve as acyl donors in the biosynthesis of gallotannins. 相似文献
29.
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