title: Biophysical study of a molecular intermediate preceding collapse of tight couple and Kaltschmidt-Wittmann ribosomes.
abstract: In previous works we evidenced, by different biophysical approaches, two levels of structural organization in Escherichia coli ribosomal particles. Thermal treatment up to a defined and non-denaturing temperature causes demolition of only one level of structural complexity. By consequence the ribosomal particle exists in an intermediate state between the native form and the completely collapsed one. In this communication we report on a structural comparison of this intermediate state in Kaltschmidt-Wittmann (LC) and 'tight couple' (TC) ribosomes. Three different biophysical approaches were adopted: dielectric spectroscopy, fluorescence and light scattering. Differential responses to thermal treatment are evidenced in the two ribosomal species. In particular TC show a more compact structure and the overall particle population is more homogeneous than LC in the native state. On the other hand, LC particles after thermal treatment undergo major alterations of geometry and/or phenomena of supra-particle aggregation.
authors.affiliation: Dipartimento di Fisica, Università La Sapienza, Piazzale Aldo Moro, 5, I-00185, Rome, Italy.
authors.forename: Adalberto
authors.initials: A
authors.lastname: Bonincontro
authors.forename: Knud H
authors.initials: KH
authors.lastname: Nierhaus
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Ortore
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Risuleo
mesh_terms: D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D055592:Biophysical Phenomena; D001703:Biophysics; D004058:Diffusion; D004926:Escherichia coli; D004996:Ethidium / Q000494:pharmacology; D006358:Hot Temperature; D008027:Light; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D012270:Ribosomes / Q000737:chemistry* / Q000187:drug effects; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D013057:Spectrum Analysis / Q000379:methods; D013696:Temperature
chemical_list: D004996:Ethidium