title: Toward Precise Interpretation of DEER-Based Distance Distributions: Insights from Structural Characterization of V1 Spin-Labeled Side Chains.
abstract: Pulsed electron paramagnetic resonance experiments can measure individual distances between two spin-labeled side chains in proteins in the range of ∼1.5-8 nm. However, the flexibility of traditional spin-labeled side chains leads to diffuse spin density loci and thus distance distributions with relatively broad peaks, thereby complicating the interpretation of protein conformational states. Here we analyzed the spin-labeled V1 side chain, which is internally anchored and hence less flexible. Crystal structures of V1-labeled T4 lysozyme constructs carrying the V1 side chain on α-helical segments suggest that V1 side chains adopt only a few discrete rotamers. In most cases, only one rotamer is observed at a given site, explaining the frequently observed narrow distance distribution for doubly V1-labeled proteins. We used the present data to derive guidelines that may allow distance interpretation of other V1-labeled proteins for higher-precision structural modeling.
authors.affiliation: Department of Biochemistry and ‡Department of Molecular Genetics, University of Toronto , Toronto, Ontario M5S 1A8, Canada.
authors.forename: Aidin R
authors.initials: AR
authors.lastname: Balo
authors.affiliation: Department of Biochemistry and ‡Department of Molecular Genetics, University of Toronto , Toronto, Ontario M5S 1A8, Canada.
authors.forename: Hannes
authors.initials: H
authors.lastname: Feyrer
authors.affiliation: Department of Biochemistry and ‡Department of Molecular Genetics, University of Toronto , Toronto, Ontario M5S 1A8, Canada.
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Ernst
mesh_terms: D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D013113:Spin Labels
chemical_list: D013113:Spin Labels