Protein synthesis rhythm

Abstract

Variations of protein content and of the rate of amino acid incorporation into protein were studied for several cells types as a function of time. It was found that both characteristics displayed a definite periodicity. The evidence available suggests that this periodicity reflects the existence of a rhythm of protein synthesis. The period of this rhythm, varying between 20 min and 2–4 hr for different cell types, suggests that we are dealing with a new class of biological rhythms with a period about 1 hr; for these rhythms the term circahoralian is proposed. This class of rhythms appears to include periodic changes of cell permeability, size of the precursor pool, electric properties (for certain cell types) and the activity of several enzymes. All these rhythms represent endogenous self-oscillating processes, frequently showing no requirement for external initiation. The regulation of protein synthesis rhythm appears to occur predominantly at the cytoplasmic level and to involve interactions of circahoralian rhythms at the membranes and at the ribosomes. Rhythms are found both in non-differentiated and in maximally differentiated cells. The period may be different in different specialized cells of a given organ. The existence of functional adaptations of protein synthesis rhythm is found and some evidence for cellular “memory” in this process is obtained. Non-identity of oscillation periods for different cell types in a given tissue and different degree of synchrony might represent a basis for the temporal regulation of tissue functions.