title: Secondary and tertiary structure of bacteriorhodopsin in the SDS denatured state.
abstract: We characterized the structure of partially unfolded bacteriorhodopsin in sodium dodecyl sulfate (SDS) micelles and compared it with its in vitro refolded structure after reconstitution with dimyristoylphosphatidylcholine/3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (DMPC/CHAPS). Intrahelical and interhelical distances were mapped in the protein using strategically located spin-label pairs at helical ends, assayed by pulsed electron paramagnetic resonance spectroscopy (double electron-electron spin resonance, DEER). We find that in SDS the intrahelical end-to-end distances exhibit broad distributions, suggesting a heterogeneous ensemble of conformations with differing secondary structures. Nevertheless, a majority of the denatured population retains end-to-end distances similar to those in the native state. In contrast, the observed greatly increased interhelical distances, in addition to their very broad distributions, suggest that in the SDS micelles very little of the native tertiary structure remains.
authors.affiliation: Department of Physiology and Biophysics, University of California, Irvine, Irvine, California 92697, United States.
authors.forename: Venkatramanan
authors.initials: V
authors.lastname: Krishnamani
authors.forename: Balachandra G
authors.initials: BG
authors.lastname: Hegde
authors.forename: Ralf
authors.initials: R
authors.lastname: Langen
authors.forename: Janos K
authors.initials: JK
authors.lastname: Lanyi
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism; D008823:Micelles; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry / Q000494:pharmacology; D019097:Spin Trapping
chemical_list: D008823:Micelles; D012967:Sodium Dodecyl Sulfate; D001436:Bacteriorhodopsins