title: Rotational and translational dynamics of ras proteins upon binding to model membrane systems.
abstract: Plasma-membrane-associated Ras proteins typically control signal transduction processes. As nanoclustering and membrane viscosity sensing provide plausible signaling mechanisms, determination of the rotational and translational dynamics of membrane-bound Ras isoforms can help to link their dynamic mobility to their function. Herein, by using time-resolved fluorescence anisotropy and correlation spectroscopic measurements, we obtain the rotational-correlation time and the translational diffusion coefficient of lipidated boron-dipyrromethene-labeled Ras, both in bulk Ras and upon membrane binding. The results show that the second lipidation motif of N-Ras triggers dimer formation in bulk solution, whereas K-Ras4B is monomeric. Upon membrane binding, an essentially free rotation of the G-domain is observed, along with a high lateral mobility; the latter is essentially limited by the viscosity of the membrane and by lipid-mediated electrostatic interactions. This high diffusional mobility warrants rapid recognition-binding sequences in the membrane-bound state, thereby facilitating efficient interactions between the Ras proteins and scaffolding or effector proteins. The lipid-like rapid lateral diffusion observed here complies with in vivo data.
authors.affiliation: Physical Chemistry I-Biophysical Chemistry, Faculty of Chemistry and Chemical Biology, TU Dortmund University, Otto-Hahn-Str. 6, 44227 Dortmund (Germany), Fax: (+49) 231 755 3901.
authors.forename: Alexander
authors.initials: A
authors.lastname: Werkmüller
authors.forename: Gemma
authors.initials: G
authors.lastname: Triola
authors.forename: Herbert
authors.initials: H
authors.lastname: Waldmann
authors.forename: Roland
authors.initials: R
authors.lastname: Winter
mesh_terms: D001896:Boron Compounds / Q000737:chemistry; D005454:Fluorescence Polarization; D008565:Membrane Proteins / Q000737:chemistry*; D008954:Models, Biological; D011485:Protein Binding; D018631:ras Proteins / Q000737:chemistry*
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D008565:Membrane Proteins; D018631:ras Proteins
keywords: diffusion; enzymes; fluorescence; lipids; proteins