Influence of Polyamine Limitation on the Chain Growth Rates of β-Galactosidase and of Its Messenger Ribonucleic Acid

Abstract

The rates of elongation of β-galactosidase and its messenger ribonucleic acid (RNA) were estimated in a polyamine-deficient mutant of Escherichia coli through an analysis of the kinetics of enzyme induction. The chain growth of β-galactosidase was calculated from the time required after the appearance of an amino terminal fragment of 60 amino acids (auto-α) until completed enzyme began to accumulate. The elongation rate of β-galactosidase messenger RNA was estimated from the time after induction at which streptolydigen-resistant, enzyme-forming capacity first appeared. Upon polyamine starvation, the rate of polypeptide elongation slowed from 17 to 10 amino acids per s and the messenger RNA elongation rate decreased from 47 to 30 nucleotides per s. These reductions in polymerization rates were proportional to the decrease in cellular growth rate produced by polyamine starvation. It was concluded that, although it is quite unlikely that polyamine levels are involved in regulation of cell growth, they may be acting as cofactors in the synthesis of RNA or protein, or both.