The membrane-targeting-sequence motif is required for exhibition of recessive resurrection in Escherichia coli RNase E

The essential homo-tetrameric endoribonuclease RNase E of Escherichia coliparticipates in global RNA turnover as well as stable RNA maturation. The protomer'sN-terminal half (residues 1-529) bears the catalytic, allosteric and tetramerizationdomains, including the critical active site residues D303 and D346. The C-terminal half(CTH, residues 530-1061) is dispensable for viability. We have previously described aphenomenon of recessive resurrection in RNase E that requires the CTH, wherein thewild-type homo-tetramer apparently displays nearly identical activity in vivo as a hetero-tetramer comprised of three catalytically dead subunits (with D303A/D346Asubstitutions) and one wild-type subunit. Here we show that recessive resurrection isexhibited even in dimeric RNase E with the CTH, and that it is largely dependent onpresence of the membrane-targeting-sequence motif (residues 565-582). A singleF575E substitution also impaired recessive resurrection, whereas other CTH motifs(such as those for binding of RNA or of partner proteins) were dispensable. Thephenomenon was independent of RNA 5'-monophosphate sensing by the enzyme. Wepropose that membrane-anchoring of RNase E renders it processive forendoribonucleolytic action, and that recessive resurrection and dominant negativityassociated with mutant protomers are mutually exclusive manifestations of,respectively, processive and distributive catalytic mechanisms in a homo-oligomericenzyme.