A PROTEIN COMPLEX MEDIATING MESSENGER-RNA DEGRADATION IN ESCHERICHIA-COLI

mRNA degradation in Escherichia coli is mediated by a combination of e xo- and endoribonucleases. We present evidence for a multiprotein comp lex which includes at least two enzymes that play important roles in m RNA degradation: the exoribonuclease polynucleotide phosphorylase (PNP ase) and the endoribonuclease RNase E. An activity which impedes the p rocessive activity of PNPase at stem-loop structures also appears to b e associated with the complex. This complex is estimated to have a mol ecular mass of about 500 kDa and includes several additional polypepti des whose functions are unknown. The identification of a complex which includes several activities associated with mRNA degradation has impl ications for the mechanisms and co-ordinated control of mRNA degradati on.