guanosine-triphosphate and cesium-chloride

Treatment of 30S-5SRNP with 1 M Cs(2)SO(4) at 2 degrees C overnight followed by sucrose density-gradient centrifugation yielded particles smaller than 30S-5SRNP, designated as CsS-particles. CsCl density-gradient centrifugation of CsS-particles showed the homogeneity of the particles containing about half the amount of proteins in 30S-5SRNP particles. The particles contained 18SrRNA, 5SRNP and about half the number of proteins in 30S-5SRNP. The ATPase activity of freshly prepared CsS-particles was about half the original 30S-5SRNP level although it was unstable even at 2 degrees C. Poly(U) slightly enhanced the activity, and phe-tRNA(phe) stimulated it concentration-dependently. EF-1a alone enhanced it, and in combination with poly(U) and phe-tRNA(phe) stimulated it markedly. EF-2 alone markedly increased it. The activity with the full components for elongation described above became very high, being comparable to that of the original 30S-5SRNP and twice that of 40S subunits. A two-dimensional electrophoretogram of the protein in CsS-particles revealed 9 small subunit protein species, in addition to L5, which included proteins interacting with mRNA and two elongation factors. Taken together with the results of our preceding study indicating the participation of ATPase of 80S ribosomes in peptide elongation, the present results indicate CsS-particles may be a part of the ATPase centre of 80S ribosomes.

Topics: Adenosine Triphosphatases; Adenosine Triphosphate; Animals; Centrifugation, Density Gradient; Cesium; Chlorides; Electrophoresis, Polyacrylamide Gel; Guanosine Triphosphate; Liver; Peptide Elongation Factors; Protein Biosynthesis; Rats; Ribosomal Proteins; Ribosomes; RNA; Sucrose

Rubidium and cesium chlorides accelerated cAMP synthesis in rat brain cortex membranes, while other alkali metal chlorides had no influence on the rate of this process. The effect was dose-dependent and yielded above 2-fold activation of adenylate cyclase. It has been shown that Rb+ and Cs+ influenced directly the catalytic subunit of the enzyme and did not substitute Mg2+ in formation of the metal-ATP complex in this reaction. The stimulatory effect of Rb+ was additive to the activation of adenylate cyclase by the half-maximal (0.3 microM) as well as by the saturating (10 microM) forskolin concentrations, pointing to the fact that these effectors activate different isoforms of the enzyme in rat brain cortex.

Topics: Animals; Cerebral Cortex; Cesium; Chlorides; Colforsin; Cyclic AMP; Dose-Response Relationship, Drug; Enzyme Activation; Guanosine Triphosphate; In Vitro Techniques; Magnesium Chloride; Rats; Rubidium