On the control mechanism of bacterial growth by cyclic adenosine 3',5'-monophosphate

Inhibition of E. coli growth by cyclic adenosine monophosphate is observed in wild type strains cultured in glucose as carbon source, but not in a cyclic AMP receptor protein deficient mutant. A deletion mutant of the adenylate cyclase gene requires cyclic adenosine monophosphate for optimal growth. Using glucose as carbon source, 2 mM cyclic AMP promotes maximal rates of cell multiplication in this mutant; however higher concentrations of the nucleotide inhibit growth. Cell multiplication of wild type strains grown in glycerol is not affected by cyclic adenosine monophosphate. Nevertheless, in this carbon source the growth rate of the adenylate cyclase mutant is strongly inhibited by concentrations of this nucleotide beyond 0.1 mM. This suggests that growth inhibition by exogenous cyclic adenosine monophosphate is highly dependent on the intracellular levels of the nucleotide.     

Lipid bilayers and liposomes in reconstitution experiments with cholinergic proteolipid from torpedo electroplax

The cholinergic proteolipid from $\text{Torpedo}$ electroplax was used in reconstitution experiments in artificial membranes being incorporated directly into the membrane-forming solution or into liposomes (proteoliposomes) which interacted with lecithin bilayers. In both cases the membrane became reactive to acetylcholine by a decrease in resistance and an increase in the frequency and amplitude of minute current fluctuations of 3·10^?11 to 4·10^?10mho. The injection of d-tubocurarine prod$\text{u}$ ced an increase in membrane resistance and a decrease in the amplitude of the current fluctuations. These results suggest that the cholinergic proteolipid is reconstituted in an active form in the bilayer.     

Intranuclear location of the tRNA splicing enzymes

The intracellular location of the enzymes that excise tRNA intervening sequences and subsequently religate the molecule was investigated in Xenopus oocytes. All the splicing activity detected in a whole oocyte was present in the nucleus. By manual separation of the nuclear envelope and the nuclear contents (which form a gel-like structure in the presence of Mg⁺⁺) it was found that all the activity of both splicing enzymes was located in the nuclear contents and was not associated with the nuclear membrane.