Functional interaction of heat shock protein GroEL with an RNase E-like activity in Escherichia coli

Abstract

The highly specific endoribonuclease activities of RNase E (which processes ribosomal 9S RNA into p5S RNA) and RNase K (which initiates decay of the ompA mRNA) are inferred to play a central role in RNA processing and mRNA decay in Escherichia coli. In vivo both activities are affected by a conditional mutation of the ams/rne gene that seems to be complemented at nonpermissive temperatures by a fragment of the groEL gene. Analysis of the relationship between the two nucleases and the heat shock protein revealed that GroEL interacts functionally with an RNase E-like activity but not with an RNase K activity, a groEL mutation affected 9S RNA processing but not ompA mRNA cleavage, RNase E activity could be precipitated with an antibody against GroEL, and a highly purified GroEL preparation contained RNase E activity but not RNase K activity. When purifying RNase E activity, we obtained a preparation containing two major proteins of 60 and 17 kDa. The size and the N-terminal sequence identified the 60-kDa protein as GroEL.