Self-Assembly of the Bacterial Cytoskeleton-Associated RNA Helicase B Protein into Polymeric Filamentous Structures

Abstract

The Escherichia coli RNA degradosome proteins are organized into a helical cytoskeletal-like structure within the cell. Here we describe the ATP-dependent assembly of the RhlB component of the degradosome into polymeric filamentous structures in vitro, which suggests that extended polymers of RhlB are likely to comprise a basic core element of the degradosome cytoskeletal structures.

Subcellular localization of RNA degrading proteins and protein complexes in prokaryotes

“…11,32 RhlB is capable of forming filaments. 33 Chromosomally encoded mRNAs remain in the vicinity of their genetic loci. 13 (C) Localization of RNase R, RNase e, tmRNA and mRNAs in C. crescentus.…”

“…11,32 RhlB itself can assemble in filaments in an ATP-dependent manner, but it is not clear whether it interacts with the membrane or with some structure beneath the membrane. 33 The molecular interactions responsible for the appearance of the membrane-bound RNase E in cytoskeleton-like structures are not known.…”

“…1B). 33,34 PNPase is structurally and functionally similar to the archaeal exosome: both degrade RNA phosphorolytically in 3'-5' direction and are responsible for the synthesis of heteropolymeric tails, which can be used as loading platforms in the process of RNA degradation. 6,15,35 In vitro, changes in the concentration of NDPs and phosphate influence the opposite activities of prokaryotic PNPase and of the archaeal exosome as RNases or RNA tailing enzymes.…”

The Price of Tags in Protein Localization Studies

“…Taking another look at some of the reported localization patterns, they could also be consistent with a distribution of patches along the membrane that could be imagined as a helical pattern, like much of the recent MreB patch localization data. As with MreB, the ability of some of these proteins to polymerize in vitro, such as RhlB (RNA helicase B) (29), may mean either that large in vivo polymers are physiologically relevant or that such polymers are artifacts of protein tags or altered stoichiometries.…”

Current perspectives of the Escherichia coli RNA degradosome

“…It has been confirmed that the RNA degradosome is structured as ordered helical elements arranged in a coil resembling cytoskeletal-elements around the cell cylinder (Taghbalout and Yang 2010). The amphipathic a-helix Segment A that anchors RNase E to the phospholipid bilayer of the cytoplasmic membrane was shown to lie within a newly proposed domain of RNase E, termed the cytoskeletal localization domain (residues 418-602) that is required for the formation of helical cytoskeletal structures .…”