RNase E, an RNA Processing Enzyme from Escherichia coZi*

An activity, RNase E, was purified about loo-fold from Escherichiu coli cells, it can process p5 rRNA from a 9 S RNA molecule which accumulates in a mutant of E. coli defective in the maturation of 5 S rRNA. The enzyme requires Na+, K+, or NH,+, and M&+ or Mn”. The molecular weight of the enzyme is about 70,000 and its pH optimum is 7.6 to 8.0. Its temperature optimum is around 3O”C, and it can be irreversibly inactivated at 50°C. It has a very high degree of specificity but the reaction can be inhibited by nonspecific RNAs. We interpret its mode of action in producing p5 RNA as being accomplished in two steps, 9 S RNA is first processed to 7 S and 4 S, and subsequently 7 S is further processed to p5.