Isolation and Characterization of a Growth‐Cycle‐Reflecting, High‐Molecular‐Weight Protein Associated with Escherichia coli Ribosomes

Abstract

A high-MW, acidic protein whose amount per ribosomal particle depends on the growth cycle is associated with E. coli ribosomes. The protein is associated with ribosomes from cells harvested at different phases of the growth cycle, but a large increase in its amount is seen with ribosomes from post-exponential phase cells. The protein is only slightly washed off [from] the ribosomes by 1 M NH4Cl. When ribosomes are dissociated it remains entirely with the 30 S subunits. The protein was purified to homogeneity. It has a MW of 70,000, and its amino acid composition showed some resemblance to that of ribosomal protein S1, but the 2 proteins are different. These results, together with the variation in the acetylation of [ribosomal protein] L12 during the growth cycle, indicate that certain proteins of (or associated with) E. coli ribosomes may carry specific biochemical roles connected with cellular adaption toward the stationary phase.