Characteristics of in vivo nitráte reductase (NR, EC 1.6.6.1) activity in leaf tissue of the crassulacean acid metabolism (CAM) plant Notonia grandiflora DC. were determined. The pH optimum for the enzyme was 7.0. Among the five low molecular mass solvents tested, n-propanol was more effective in promoting NR activity. Supply of 1.0 % (v/v) M-propanol along with 0.5 % Triton X-100 was the most appropriate assay condition to bring about maximum NR activity (NRA), that was proportionally enhanced with duration of the incubation and mass of the leaf tissue. Leaf fragments of 2 to 4 mm slice width had maximal NRA. The highest NRA was obtained with 200 mM of nitráte supplied in the infiltration medium. NRA was higher in fully expanded, mature leaves than in tender and senescing leaves. The cellular nitráte content was strongly positively correlated with NRA in leaves of various physiological ages. The NRA/N03’ content ratio (index of nitráte utilization efQciency) was the highest for the tender leaves and the lowest for the senescing leaves. However, maximum total titratable acidity (malate production) was obtained for the fully expanded mature leaves in comparison with the other leaves. A positive and significant correlation (r = 0.92) was obtained between nitráte reduction and titratable acid content. The results are indicative of a possible role of nitráte reduction in the regulation of noctumal acid production in the CAM plants.
Microsporidia are eukaryotic, obligate intracellular organisms defined by their small spores containing a single polar tube that coils around the interior of the spore. After appropriate stimuli the germination of spores occurs. Conditions that promote germination vary widely among species, presumably reflecting the organism’s adaptation to their host and external environment as well as preventing accidental discharge in the environment. It appears that calcium may be a key ion in this process. Regardless of the stimuli required for activation, all microsporidia exhibit the same response to the stimuli, that is, increasing the intrasporal osmotic pressure. This results in an influx of water into the spore accompanied by swelling of the polaroplasts and posterior vacuole. The polar tube then discharges from the anterior pole of the spore in an explosive reaction and is thought to form a hollow tube by a process of eversion. If the polar tube is discharged next to a cell, it can pierce the cell and transfer the sporoplasm into this cell. Polar tubes resist dissociation in detergents and acids but dissociate in dithiothreitol. We have developed a method for the purification of polar tube proteins (PTPs) using differential extraction followed by reverse phase high performance liquid chromatography (HPLC). This method was used to purify for subsequent characterization PTPs from Glugea americanus, Encephalitozoon cuniculit E. hellem and E. intestinalis. These proteins appear to be members of a protein family that demonstrate conserved characteristics in solubility, hydrophobicity, mass, proline content and immunologic epitopes. These characteristics are probably important in the function of this protein in its self assembly during the eversion of the polar tube and in providing elasticity and resiliency for sporoplasm passage.
The rod-like structures containing ribosome particles isolated from cell membranes of the cyanobacterium Phormidium laminosum were sensitive to RNAase and capable to incoiporate in viíro ■'♦C-amino acids into polypeptides. These facts can be considered as an evidence for the presence of protein-synthesizing apparatus in the rod-like structures of cyanobacterial membranes.
The photosynthetic election transport activities in beet spinách thylakoids were studied using ruthenium chloride as an electron acceptor, Like potassium ferricyanide, RUCI3 supported the non-cyclic electron flow with net evolution of oxygen. The rate of oxygen evolution was at its maximum with 0.5 mM RUCI3 at pH of 8.0 and the election flow coupled to translocation of protons into the thylakoid vesicles. Ruthenium chloride-supported oxygen evolution was inhibited by specific photosynthetic electron tiansport inhibitors like diuron, dibromothymoquinone, potassium cyanide, and mercuric chloride Unlike ferricyanide, the RuCl3-supported oxygen evolution was totally inliibited by potassium cyanide and mercuric chloride at both pH 8.0 and 6.5. Since potassium cyanide and mercuric chloride mostly interrupt the electron flow at plastocyanin level, RUCI3 probably accepts electrons mostly from photosystem 1 or its near vicinity. Besides electron acceptance, RUCI3 suppresses the photophosphoiylation activity in a manner similar to energy transfer inhibitors.