STRUCTURE AND FUNCTION OF E. coli RIBOSOMES, VIII. COLD-SENSITIVE MUTANTS DEFECTIVE IN RIBOSOME ASSEMBLY

Abstract
E. coli mutants that fail to grow at 20°C were isolated, and three such mutants were studied in detail. Two of these are defective in 50 S ribosome biosynthesis at low temperatures and accumulate 43 S and 32 S particles, respectively. The third mutant produces reduced amounts of 50 S ribosomes and accumulates 21 S particles at low temperatures. The 43 S and 32 S particles contain 23 S RNA and appear to be precursors of 50 S ribosomes. The 21 S particles contain 16 S RNA. The mutation that causes accumulation of 32 S particles is linked to the spc locus. Isolation and characterization of coldsensitive mutants should provide a fruitful approach to the study of in vivo ribosomal assembly.