An essential function of ribosomal protein S1 in mRNA translation

Abstract

A gentle and efficient method for selectively removing S1 from [Escherichia coli] ribosomes was developed: the S1-free translation system prepared from such ribosomes is stimulated 10- to 20-fold (depending on the mRNA) by a stoichiometric amount of added purified S1. With this system, the activity of mono- and di-N-ethylmaleimide derivatives of S1 in protein synthesis was examined using synthetic and natural mRNA and electrophoretic analysis of the translation products. The results show that ribosomes containing such modified S1 are functionally active although at a somewhat lower level (50-80% activity). Since treatment of S1 with N-ethylmaleimide abolishes the helix-destabilizing ability of S1, this ability apparently is not primarily responsible for S1 biological function. A new model for the role of S1 is proposed on the basis of the physical, structual and RNA-binding properties of S1.