Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 20

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Nitrate and nitrite reduction centers in nonnodulated and symbiotic yellow lupine were analyzed. In young seedlings, nitrate was exclusively accumulated in roots, which also was shown as the main nitrate reduction center. In contrast, leaves were shown to play a key role in nitrite reduction. A similar distribution of nitrate reductase (NR) and nitrite reductase was found in nodulated plants. However, in field conditions characterized by low nitrate content, a disproportionately high level of NR activity in nodules was also observed during all stages of symbiotic growth. This feature was confirmed in nitrate-fed hydroponic cultures. Nodule NR activity was one order of magnitude higher than in roots, in spite of the small stored nitrate pool found inside nodules. This suggests that nodule NR activity had been induced not by nitrate itself but indirectly. Since bacteroids were shown to be responsible for the vast majority of nodule NR activity, the plausible explanation of this effect seems to be a dissimilatory nature of rhizobial NR. Considering that environmental nitrate could cause hypoxia inside nodules, this is the proposed way of the observed nodule NR induction.
The thylakoid protease AtDeg2 is a non-ATP hydrolyzing chloroplast protease/ chaperone peripherally connected with stromal side of thylakoid membrane. Its linear structure consists of protease domain and two PDZ domains. To unveil the significance of individual domains, chaperone and proteolytic activities of AtDeg2, its mutated recombinant versions have been developed and their ability to suppress protein aggregation and resolubilization of protein aggregates as well as the ability to degrade substrate protein was examined in vitro. Our work reveals for the first time that AtDeg2 is able not only to suppress aggregation of denatured proteins, but to resolubilize existing protein aggregates as well. We show that PDZ2 domain contributes significantly to both chaperone and protease activities of AtDeg2, whereas PDZ1 is required for chaperone but superfluous for proteolytic activity. Protease domain – but not S-268 in its catalytic site – contributes to chaperone activities of AtDeg2. These results show an entirely new function of AtDeg2 chaperone/protease (i.e., disaggregation of protein aggregates) and allow to identify structural motifs required for “old” and new functions of AtDeg2.
AtDeg2 is a chloroplast protein with dual protease/chaperone activity. Since data on how the individual activities of AtDeg2 affect growth and development of Arabidopsis thaliana plants is missing, two transgenic lines were prepared that express mutated AtDeg2 versions that have either only protease or chaperone activity and a comprehensive ontogenesis stage-based study was performed comprising wild type (WT) plants and insertional mutants that do not express AtDeg2, as well as the two transgenic lines. The repression of both AtDeg2 activities in deg2-3 mutants altered just a few phenotypic traits including the time when cotyledons were fully opened, the time when 10% flowers were open as well as the number of inflorescence branches and seed length in plants which have completed their generative development. It was demonstrated that complete opening of cotyledons as well as the number of inflorescence branches and seed length in plants which have completed their generative development required involvement of both AtDeg2 activities, whereas the time when 10% of flowers were open was controlled by AtDeg2 protease activity. These results show for the first time that the chaperone activity of AtDeg2 is needed for some elements of generative development of A. thaliana plants to proceed normally. So far, the chaperone activity of AtDeg2 was confirmed based on in vitro assays only.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.