Mechanism of protein biosynthesis in prokaryotic cells

Abstract

To define the step at which translational initiation factor IF1 excercises its stimulation, initial rate kinetic analyses of 30 S initiation complex formation were carried out in the presence and absence of this factor. It was shown that, without affecting the affinity of the ribosomes either for the initiator tRNA or for the poly(AUG) used as template, IF1 increases approximately 2.5-fold the limiting V _maxof the ‘pre-ternary complex’ ← ternary complex transition which represents the rate-limiting step in 30 S initiation complex formation. This kinetic effect titrates with the 30 S ribosomal subunit which must therefore represent the target of IF1 action.