title: Quaternary structure and catalytic activity of the Escherichia coli ribonuclease E amino-terminal catalytic domain.
abstract: RNase E is an essential endoribonuclease that plays a central role in the processing and degradation of RNA in Escherichia coli and other bacteria. Most endoribonucleases have been shown to act distributively; however, Feng et al. [(2002) Proc. Natl. Acad. Sci. U.S.A. 99, 14746-14751] have recently found that RNase E acts via a scanning mechanism. A structural explanation for the processivity of RNase E is provided here, with our finding that the conserved catalytic domain of E. coli RNase E forms a homotetramer. Nondissociating nanoflow-electrospray mass spectrometry suggests that the tetramer binds up to four molecules of a specific substrate RNA analogue. The tetrameric assembly of the N-terminal domain of RNase E is consistent with crystallographic analyses, which indicate that the tetramer possesses approximate D(2) dihedral symmetry. Using X-ray solution scattering data and symmetry restraints, a solution shape is calculated for the tetramer. This shape, together with limited proteolysis data, suggests that the S1-RNA binding domains of RNase E lie on the periphery of the tetramer. These observations have implications for the structure and function of the RNase E/RNase G ribonuclease family and for the assembly of the E. coli RNA degradosome, in which RNase E is the central component.
authors.affiliation: Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge CB2 1GA, UK.
authors.forename: Anastasia J
authors.initials: AJ
authors.lastname: Callaghan
authors.forename: J Günter
authors.initials: JG
authors.lastname: Grossmann
authors.forename: Yulia U
authors.initials: YU
authors.lastname: Redko
authors.forename: Leopold L
authors.initials: LL
authors.lastname: Ilag
authors.forename: Martin C
authors.initials: MC
authors.lastname: Moncrieffe
authors.forename: Martyn F
authors.initials: MF
authors.lastname: Symmons
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: McDowall
authors.forename: Ben F
authors.initials: BF
authors.lastname: Luisi
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D020134:Catalytic Domain; D002918:Chymotrypsin / Q000737:chemistry; D003460:Crystallization; D004722:Endoribonucleases / Q000737:chemistry*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry; D036103:Nanotechnology; D010446:Peptide Fragments / Q000737:chemistry*; D011117:Polyribonucleotide Nucleotidyltransferase / Q000737:chemistry; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D021241:Spectrometry, Mass, Electrospray Ionization; D014965:X-Rays
chemical_list: D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; D010446:Peptide Fragments; D011994:Recombinant Proteins; C111244:degradosome; D011117:Polyribonucleotide Nucleotidyltransferase; D004722:Endoribonucleases; C022537:ribonuclease E; D002918:Chymotrypsin; D020365:RNA Helicases