Ionic regulation in genetic translation systems.

The polyelectrolyte theory can provide an interpretation of the interdependence of pH, ionic strength, and polyamines one observes in the activity of ribonuclease acting on RNA. According to this theory: (i) A nucleic acid-enzyme complex and the suspending medium may be considered as two phases in equilibrium, even though within limits, the complex is soluble in water. (ii) The enzymatic catalysis is under tight control of the electrostatic potential generated by the system. Consequently, modification in electrostatic potential will induce a concomitant change in activity. (iii) The electrostatic potential can be modified through action on the system of "modulators", either "external" (ionic strength, pH, temperature, etc.) or "internal" (specific ligands, substrates, protein factors, etc.). Similarities between the reaction of ribonuclease (ribonuclease 3'-pyrimidino-oligonucleotidohydrolase; EC 3.1.4.22) and RNA and those observed with highly organized systems catalyzing DNA, RNA, and protein synthesis suggest that the electrostatic potential also provides an important regulatory mechanism in genetic translation. In this view, an essential function of nucleic acids is to provide their enzyme partners with polyanionic microenvironments within which their catalytic activities are controlled by variation in physicochemical parameters, including the proton concentration induced through "modulation" of the local electrostatic potential.