Coordinated induction and subsequent activity changes of two groups of metabolically interrelated enzymes. Light-induced synthesis of flavonoid glycosides in cell suspension cultures of Petroselinum hortense.

The enzymes of the flavonoid glycoside pathway were specifically induced upon irradiation of a 10-day-old, dark-grown cell suspension culture of Petroselinum hortense Hoffm. with ultraviolet light. The curves for the activity changes of a first sequence of three enzymes (group I) revealed only small, but significant, differences. Sharp peaks in these enzyme activities were observed at about 17, 22, and 23 h after the onset of the irradiation. The apparent half-lives during the subsequent periods of decline ranged, in the same order, from about 10 to 15 and 17 h. No significant differences were found for the lag periods preceding the increases in the three enzyme activities. The possibility is discussed that the slight differences in the patterns of the light-induced activity changes are mainly due to different rates of degradation of the enzymes, suggesting an otherwise largely interpendent regulation. The patterns of the activity changes of four enzymes of the second sequence (group II) differed greatly from those observed for group I, but were again similar to one another. Thus, the two groups of enzymes appear to be regulated differently, despite their concomitant induction. A sigmoidal curve for the accumulation of the flavonoid glycosides was obtained upon the induction of the enzymes. This curve corresponded closely to that derived by integration of the curve for the activity changes of the first enzyme of group I, phenylalanine ammonia-lyase. It is concluded that this enzyme might be rate-limiting for the entire pathway.     

Simulation of N2O emissions from rain-fed wheat and the impact of climate variation in southeastern Australia

The Water and Nitrogen Management model (WNMM) was applied to simulate N₂O emissions from a rain-fed wheat cropping system on a loam-textured soil for two treatments, conventional cultivation with residue burn (CC?+?BURN?+?N) and direct drill with residue retention (DD?+?RET?+?N), at Rutherglen in southeastern Australia from January 2004 to March 2005. Both treatments received the same amount of nitrogen (N) fertiliser. The WNMM satisfactorily simulated the soil water content, mineral N contents and N₂O emissions from the soil, as compared with the field observations for both treatments. The simulated nitrification-induced N₂O emissions accounted for 45% and 34% of total N₂O emissions for the treatments CC?+?BURN?+?N and DD?+?RET?+?N, respectively. The calibrated WNMM was used to simulate N₂O emissions from this soil using historic daily weather data from 1968 to 2004 and applying seven scenarios of fertiliser N application. Correlation analysis found that the annual N₂O emissions for this rain-fed wheat cropping system were significantly correlated to the annual average of daily maximum air temperature (r?=?0.51 for CC?+?BURN?+?N and 0.56 for DD?+?RET?+?N), annual rainfall (r?=??0.56 for CC?+?BURN?+?N and ?0.59 for DD?+?RET?+?N) and fertiliser N application rate (r?=?0.43 for CC?+?BURN?+?N and 0.31 for DD?+?RET?+?N). Based on the 37-year historic simulations, multivariate regression models for estimating annual N₂O emissions were developed to account for climatic variation, and explained about 50% of variations of annual N₂O emissions estimated by WNMM.     

Localization of corticotropin- and endorphin-related peptides in the intermediate lobe of the rat pituitary

Summary The question is examined whether -melanocyte stimulating hormone (-MSH), adrenocorticotropic hormone (ACTH), met-enkephalin and -endorphin are detectable by enzyme immunocytochemistry in the cells of the intermediate lobe (PI) of the rat pituitary. By applying antibodies against MSH, ACTH and -endorphin on light microscopic sections, intense immunostaining was found in all PI-cells. At the ultrastructural level, after treatment of consecutive serial sections with these three antibodies the immunoreactivity was localized in the same secretory granules. No specific metenkephalin immunoreactivity could be detected in the cells of the intermediate lobe.Supported by Deutsche Forschungsgemeinschaft SFB 87/B2     

DFT study of the intrinsic conformations of [2Fe-2S-4(SCH3)] clusters and their influence on exchange coupling

We have determined the equilibrium conformations of the diiron(III) cluster [2Fe-2S-4(SCH₃)]²⁻ using density functional theory. The conformers have dihedral Fe-Fe-S-C angles of ∼0° and ±120°. The relative energies of the conformers can be accurately parameterized with a small number of side-chain repulsion parameters. Of the 17 conformers identified on the basis of the ideal values for the dihedrals, 10 conformers are stable in both the ferromagnetic and broken symmetry state for the cluster. The exchange coupling constants for the seven energetically lowest conformers are predicted to belong to a narrow range, 150 cm⁻¹ ? J ? 178 cm⁻¹. The cluster conformers found in proteins do not coincide with any of the intrinsic ones, due to distortion of one of the dihedral angles under the influence of the protein scaffold.     

Durch Phytochrom kontrollierte Enzyme der Flavonoidsynthese in Zellsuspensionskulturen von Petersilie (Petroselinum hortense Hoffm.)

Summary Enzymes involved in flavonoid synthesis in parsley (Petroselinum nortense Hoffm.) cell suspension cultures are induced by light. It has been suggested that the regulation of the enzymes of phenylpropanoid metabolism (group 1) is independent of that of the enzymes of flavonoid synthesis proper (group 2) [Hahl-brock, K., Ebel, J., Ortmann, R., Sutter, A., Wellmann, E., Grisebach, H.: Biochim. biophys. Acta (Amst.) 244, 7–15 (1971)]. Phytochrome was demonstrated to be involved in the light effect controlling flavonoid synthesis. Phytochrome is only effective after a preceding irradiation with ultraviolet light (_max<300 nm) [Wellmann, E.: Planta (Berl.) 101, 283–286 (1971)]. — In order to determine whether phytochrome affects phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), a group 1 enzyme, or exerts a general effect of all enzymes of the flavonoid pathway. PAL and two enzymes from group 2, chalcone-flavanone isomerase and UDP-apiose synthetase, were investigated. Under appropriate conditions of irradiation (low UV-dose with subsequent red/far-red pulses) both group 2 enzymes were shown to be controlled by phytochrome to the same extent as PAL. The UV-induced increase in activity of all three enzymes is reduced to about 70% by an irradiation for 10 min with far-red light. This far-red effect is fully reversible by a subsequent irradiation with 10 mith red light. There is no evidence for a rate limiting enzyme (or group of enzymes) involved in flavonoid formation with respect to phytochrome control.

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Abkürzungen PAL Phenylalaninammoniumlyasc - CFI Chalkonflavanonisomerase     

Characterization of the New World monkey homologues of human poliovirus receptor CD155

In contrast to Old World monkeys, most New World monkeys (NWMs) are not susceptible to poliovirus (PV), regardless of the route of infection. We have investigated the molecular basis of restricted PV pathogenesis of NWMs with two kidney cell lines of NWMs, TMX (tamarin) and NZP-60 (marmoset), and characterized their PV receptor homologues. TMX cells were susceptible to infection by PV1 (Mahoney) and PV3 (Leon) but not by PV2 (Lansing). Binding studies to TMX cells indicated that the formation of PV/receptor complexes increased when measured first at 4 degrees C and then at 25 degrees C, whereas PV2 did not significantly bind to TMX cells at either temperature. On the other hand, NZP-60 cells were not susceptible to infection by any of the PV serotypes. However, a low amount of PV1 bound to NZP-60 cells at 4 degrees C, but there was no increase of binding at 25 degrees C. In contrast, both NWM cell lines supported genome replication and virion formation when transfected with viral RNAs of either serotype, an observation indicating that infection was blocked in receptor-virus interaction. To overcome the receptor block, we substituted 3 amino acids in the marmoset receptor (nCD155), H80Q, N85S, and P87S, found in the human PV receptor, hCD155. Cells expressing the mutant receptor (L-nCD155mt) were now susceptible to infection with PV1, which correlated with an increase in PV1-bound receptor complexes from 4 degrees C to 25 degrees C. L-nCD155mt cells were, however, still resistant to PV2 and PV3. These data show that an increase in the formation of PV/receptor complexes, when measured at 4 degrees C and at 25 degrees C, correlates with and is an indicator of successful infection at 37 degrees C, suggesting that the complex formed at 25 degrees C may be an intermediate in PV uptake.     

The crystal structure of coxsackievirus A21 and its interaction with ICAM-1

CVA21 and polioviruses both belong to the Enterovirus genus in the family of Picornaviridae, whereas rhinoviruses form a distinct picornavirus genus. Nevertheless, CVA21 and the major group of human rhinoviruses recognize intercellular adhesion molecule-1 (ICAM-1) as their cellular receptor, whereas polioviruses use poliovirus receptor. The crystal structure of CVA21 has been determined to 3.2 A resolution. Its structure has greater similarity to poliovirus structures than to other known picornavirus structures. Cryo-electron microscopy (cryo-EM) was used to determine an 8.0 A resolution structure of CVA21 complexed with an ICAM-1 variant, ICAM-1(Kilifi). The cryo-EM map was fitted with the crystal structures of ICAM-1 and CVA21. Significant differences in the structure of CVA21 with respect to the poliovirus structures account for the inability of ICAM-1 to bind polioviruses. The interface between CVA21 and ICAM-1 has shape and electrostatic complementarity with many residues being conserved among those CVAs that bind ICAM-1.