DEFECT IN THE SPLIT PROTEINS OF 30-S RIBOSOMAL-SUBUNITS AND UNDER-METHYLATION OF 16-S RIBOSOMAL-RNA IN A POLYAMINE-REQUIRING MUTANT OF ESCHERICHIA-COLI GROWN IN THE ABSENCE OF POLYAMINES

Polyphenylalanine synthesis was carried out with Escherichia coli Q13 50‐S ribosomal subunits and reconstituted 30‐S particles containing different combinations of 23‐S core particles and 30‐S subunit split proteins obtained from a polyamine‐requiring mutant of E. coli during its growth in the presence or absence of putrescine. It was concluded that the defect in the amount of some kinds of 30‐S subunit split proteins was responsible for the decrease of polypeptide synthesis in a polyamine‐requiring mutant of E. coli grown in the absence of polyamines. The methylation of 16‐S RNA during growth in the absence of putrescine was decreased, while the degree of methylation of 23‐S RNA did not change significantly. The decrease in methylation of 16‐S RNA in the absence of putrescine was due mainly to a decrease of methylation of adenine. The relationship between the decrease of polypeptide synthetic activity of 30‐S ribosomal subunits obtained from a polyamine‐requiring mutant of E. coli grown in the absence of polyamines and the decrease of methylation of 16‐S RNA is discussed. Copyright © 1979, Wiley Blackwell. All rights reserved