Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 98, Issue 1, Pages 63-68Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.011535498
Keywords
immunogold labeling; RhlB RNA helicase; RNA process; RNA degradation
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Funding
- NIGMS NIH HHS [R01 GM054158, GM 54158] Funding Source: Medline
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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.
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