title: Release factors 2 from Escherichia coli and Thermus thermophilus: structural, spectroscopic and microcalorimetric studies.
abstract: Prokaryotic class I release factors (RFs) respond to mRNA stop codons and terminate protein synthesis. They interact with the ribosomal decoding site and the peptidyl-transferase centre bridging these 75 A distant ribosomal centres. For this an elongated RF conformation, with partially unfolded core domains II.III.IV is required, which contrasts the known compact RF crystal structures. The crystal structure of Thermus thermophilus RF2 was determined and compared with solution structure of T. thermophilus and Escherichia coli RF2 by microcalorimetry, circular dichroism spectroscopy and small angle X-ray scattering. The structure of T. thermophilus RF2 in solution at 20 degrees C is predominantly compact like the crystal structure. Thermodynamic analysis point to an initial melting of domain I, which is independent from the melting of the core. The core domains II.III.IV melt cooperatively at the respective physiological temperatures for T. thermophilus and E. coli. Thermodynamic analyses and the X-ray scattering results for T. thermophilus RF2 in solution suggest that the compact conformation of RF2 resembles a physiological state in absence of the ribosome.
authors.affiliation: Department of Biochemistry, P. J. Safárik University Kosice, Slovakia.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Zoldák
authors.forename: Lars
authors.initials: L
authors.lastname: Redecke
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Peter V
authors.initials: PV
authors.lastname: Konarev
authors.forename: C Stefan
authors.initials: CS
authors.lastname: Voertler
authors.forename: Holger
authors.initials: H
authors.lastname: Dobbek
authors.forename: Erik
authors.initials: E
authors.lastname: Sedlák
authors.forename: Mathias
authors.initials: M
authors.lastname: Sprinzl
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010454:Peptide Termination Factors / Q000737:chemistry* / Q000302:isolation & purification; D011489:Protein Denaturation; D053838:Scattering, Small Angle; D016963:Thermus thermophilus; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D010454:Peptide Termination Factors; C489006:prfB protein, E coli