Cellular ATP Pool Research Articles

Yeast killer factor: ATP leakage and coordinate inhibition of macromolecular synthesis in sensitive cells

The action of the yeast killer factor proteins on sensitive yeast cells has been examined. The killer factor caused a coordinate inhibition of protein synthesis, nucleic acid synthesis and d-[ 4C]glucose incorporation into macromolecules in growing sensitive cells. During the inhibition period ATP became detectable in the growth medium and the cellular ATP pool level fell to exhaustion. ATP synthesis continued over this period as extracellular ATP accumulated to levels 4–20-fold those found in the cellular pools of control cultures. Leakage studies on other cellular components over the ATP leakage period indicated little loss of macromolecules, but an increased efflux of pools of leucine and glucose. The results are consistent with a killer-induced alteration in the yeast cell membrane.

The relationship between rates of [ 3H]uridine and [ 3H]adenine incorporation into RNA and the measured rates of RNA synthesis during the cell cycle

The rates of [5- 3H]uridine uptake into Chinese hamster V79 cells and its incorporation into RNA increase 10-fold during the cell cycle. In contrast, the rates of [ 3H]adenine uptake and incorporation increase only 2-fold over the same time period. The pattern of [ 3H]thymidine uptake into cells is unlike that of either [5- 3H]uridine or [ 3H]adenine, suggesting that transport of each of these nucleic acid precursors behaves differently during the cell cycle. The rates of RNA synthesis during the cell cycle were measured by relating the amount of [ 3H]adenine incorporated into RNA to the specific radioactivity of the [ 3H]ATP pool at 6 different time intervals. The rate of RNA synthesis doubles during the cell cycle. The cellular ATP pool undergoes a 2-fold increase, and the specific radioactivity of the [ 3H]ATP pool remains constant. [ 3H]adenine incorporation in this system provides a better measure of RNA synthetic rate than does [ 3H]uridine.

Phosphorus availability and nitrogenase activity in aquatic blue‐green algae

SUMMARYMetabolically active phosphorus‐starved cultures of blue‐green algae assimilate 32P rapidly in the light and in the dark. The uptake of phosphorus results in a rapid (within 15 min) stimulation in acetylene reduction by Anabaena cylindrica, A. flosaquae, Anabacnopsis circuiaris and Chlorogloea fritschii, with a response being obtained to less than 5 μg/1 of phosphorus. Uptake of phosphorus also causes a rapid increase in respiration in the dark but not in photo respiration, and the size of the cellular ATP pool and the 14CO2 fixation rate both increase more slowly. The metabolism of phosphorus‐sufficient cells, which assimilate phosphorus more slowly, shows little response when phosphorus is provided.Excess phosphorus is stored in the vegetative cells of blue‐green algae as polyphosphate bodies which may form within 60 min of adding phosphorus to phosphorusstarved cells and which serve as a source of phosphorus for the algae when exogenous phosphorus is limiting. Preliminary results from Scottish waters suggest that urban effluents are important sources of available‐phosphorus for algal growth and that the levels entering fresh waters from agricultural land are, per unit volume, lower. In both types of water the levels of available‐phosphorus are rather similar to the levels of orthophosphate‐phosphorus present. Most detergents tested serve as a source of phosphorus for nitrogen‐fixing blue‐green algae and cause a rapid stimulation in reduction when added to phosphorus‐starved cultures. Of the detergents assayed, the biological types were richest in available phosphorus. The addition of detergents may result in a rapid increase in number of polyphosphate bodies present in the algae. Detergents in general also contain an inhibitor of algal metabolism. Whether a stimu‐lation or an inhibition occurs depends on the quantities of detergent added and on whether or not the alga is phosphorus‐deficient.