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661.
662.
E. Wilmowicz K. Frankowski P. Glazińska J. K?sy W. Wojciechowski J. Kopcewicz 《Biologia Plantarum》2011,55(4):757-760
Application of gibberellic acid (GA3) on the cotyledons of 5-d-old Pharbitis nil reversed the inhibitory effect of both abscisic acid (ABA) and ethylene on flowering. Application of GA3 slightly decreased ethylene production and did not affect the endogenous ABA content in the cotyledons during the night.
However, it reversed the stimulating effect of ABA on ethylene production. 相似文献
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Alexander J. F. Egan Jacob Biboy Inge van't Veer Eefjan Breukink Waldemar Vollmer 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2015,370(1679)
Peptidoglycan (PG) is an essential component in the cell wall of nearly all bacteria, forming a continuous, mesh-like structure, called the sacculus, around the cytoplasmic membrane to protect the cell from bursting by its turgor. Although PG synthases, the penicillin-binding proteins (PBPs), have been studied for 70 years, useful in vitro assays for measuring their activities were established only recently, and these provided the first insights into the regulation of these enzymes. Here, we review the current knowledge on the glycosyltransferase and transpeptidase activities of PG synthases. We provide new data showing that the bifunctional PBP1A and PBP1B from Escherichia coli are active upon reconstitution into the membrane environment of proteoliposomes, and that these enzymes also exhibit DD-carboxypeptidase activity in certain conditions. Both novel features are relevant for their functioning within the cell. We also review recent data on the impact of protein–protein interactions and other factors on the activities of PBPs. As an example, we demonstrate a synergistic effect of multiple protein–protein interactions on the glycosyltransferase activity of PBP1B, by its cognate lipoprotein activator LpoB and the essential cell division protein FtsN. 相似文献
665.
Jenny Krönström Waldemar Karlsson Bengt R. Johansson Susanne Holmgren 《Cell and tissue research》2009,336(2):299-308
Inside the light organs of the bioluminescent (light-producing) crustacean Meganyctiphanes norvegica (krill), numerous capillaries drain haemolymph into the light-producing structure (lantern). We have investigated the arrangement
and function of filamentous material found around the opening of the capillaries. These have been suggested to work as sphincters,
controlling the haemolymph (i.e. oxygen) supply to the lantern and thereby the production of light. Electron microscopy shows
that the filamentous material consists of thick and thin muscle filaments arranged in perpendicular blocks around the opening
of each capillary. The actin probe rhodamine phalloidin has revealed that one component is filamentous actin. Clusters of
vesicle-dense nerve profiles surround the cells containing filamentous material and antibodies against 5-hydroxytryptamine
(5-HT) reveal that 5-HT containing nerves lead to the filamentous area. When exposed to the muscle-relaxing substances papaverine
and verapamil, krill respond with luminescence, suggesting that the sphincter structures are functionally involved in the
control of light production. Treatment with the muscle-contracting drugs Bay K8544 and thapsigargin gives no light response.
Thus, 5-HT stimulates light production in krill; however, a combination of 5-HT and the muscle-relaxing drugs or Bay K8544
potentiates the effect of 5-HT. Thapsigargin quenches the response to 5-HT. Our results corroborate speculations of earlier
authors who have suggested that the sphincter structures are of a muscular nature and important in controlling light production
in krill. However, other parameters in addition to the oxygen supply to the lantern are involved in controlling bioluminescence
in the light organs of M. norvegica.
We acknowledge financial support from the Biodiversity Program of the Swedish Science Research Council and from the Royal
Swedish Academy of Science for supporting work at the Kristineberg Marine Research Center. Electron microscopy equipment was
granted by the Lundberg Research Foundation. 相似文献
666.
Cheryl L. Wojciechowski Evan R. Kantrowitz 《Biochimica et Biophysica Acta - Proteins and Proteomics》2003,1649(1):68-73
Four independent mutations were introduced to the Escherichia coli alkaline phosphatase active site, and the resulting enzymes characterized to study the effects of Glu as a metal ligand. The mutations D51E and D153E were created to study the effects of lengthening the carboxyl group by one methylene unit at the metal interaction site. The D51E enzyme had drastically reduced activity and lost one zinc per active site, demonstrating importance of the position of Asp51. The D153E enzyme had an increased kcat in the presence of high concentrations of Mg2+, along with a decreased Mg2+ affinity as compared to the wild-type enzyme. The H331E and H412E enzymes were created to probe the requirement for a nitrogen-containing metal ligand at the Zn1 site. The H331E enzyme had greatly decreased activity, and lost one zinc per active site. In the absence of high concentrations of Zn2+, dephosphorylation occurs at an extremely reduced rate for the H412E enzyme, and like the H331E enzyme, metal affinity is reduced. Except at the 153 position, Glu is not an acceptable metal chelating amino acid at these positions in the E. coli alkaline phosphatase active site. 相似文献
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Olga Flegontova Pavel Flegontov Paula Andrea Castañeda Londoño Waldemar Walczowski Danijela Šantić Virginia P. Edgcomb Julius Lukeš Aleš Horák 《Environmental microbiology》2020,22(9):4014-4031
We analysed a widely used barcode, the V9 region of the 18S rRNA gene, to study the effect of environmental conditions on the distribution of two related heterotrophic protistan lineages in marine plankton, kinetoplastids and diplonemids. We relied on a major published dataset (Tara Oceans) where samples from the mesopelagic zone were available from just 32 of 123 locations, and both groups are most abundant in this zone. To close sampling gaps and obtain more information from the deeper ocean, we collected 57 new samples targeting especially the mesopelagic zone. We sampled in three geographic regions: the Arctic, two depth transects in the Adriatic Sea, and the anoxic Cariaco Basin. In agreement with previous studies, both protist groups are most abundant and diverse in the mesopelagic zone. In addition to that, we found that their abundance, richness, and community structure also depend on geography, oxygen concentration, salinity, temperature, and other environmental variables reflecting the abundance of algae and nutrients. Both groups studied here demonstrated similar patterns, although some differences were also observed. Kinetoplastids and diplonemids prefer tropical regions and nutrient-rich conditions and avoid high oxygen concentration, high salinity, and high density of algae. 相似文献
670.