RNA degradosomes exist in vivo in Escherichia coli as multicomponent complexes associated with the cytoplasmic membrane via the N-terminal region of ribonuclease E.
RNase E isolated from Escherichia coli is contained in a multicomponent "degradosome" complex with other proteins implicated in RNA decay. Earlier work has shown that the C-terminal region of RNase E is a scaffold for the binding of degradosome components and has identified specific RNase E segments necessary for its interaction with polynucleotide phosphorylase (PNPase), RhlB RNA helicase, and enolase. Here, we report electron microscopy studies that use immunogold labeling and freeze-fracture methods to show that degradosomes exist in vivo in E. coli as multicomponent structures that associate with the cytoplasmic membrane via the N-terminal region of RNase E. Whereas PNPase and enolase are present in E. coli in large excess relative to RNase E and therefore are detected in cells largely as molecules unlinked to the RNase E scaffold, immunogold labeling and biochemical analyses show that helicase is present in approximately equimolar amounts to RNase E at all cell growth stages. Our findings, which establish the existence and cellular location of RNase E-based degradosomes in vivo in E. coli, also suggest that RNA processing and decay may occur at specific sites within cells.
Liou
G G
GG
Institute of Molecular Biology, Academia Sinica, Nankang, Taipei 115, Taiwan.
Jane
W N
WN
Cohen
S N
SN
Lin
N S
NS
Lin-Chao
S
S
D001426:Bacterial Proteins / Q000378:metabolism / Q000648:ultrastructure; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D004722:Endoribonucleases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure*; D004926:Escherichia coli / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D005614:Freeze Fracturing; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure*; D011117:Polyribonucleotide Nucleotidyltransferase / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure*; D011485:Protein Binding; D020365:RNA Helicases / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure*; D012329:RNA, Bacterial / Q000378:metabolism*
D001426:Bacterial Proteins; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D012329:RNA, Bacterial; C111244:degradosome; D011117:Polyribonucleotide Nucleotidyltransferase; D004722:Endoribonucleases; C022537:ribonuclease E; D020365:RNA Helicases