title: Three-dimensional structure of myelin basic protein. I. Reconstruction via angular reconstitution of randomly oriented single particles.
abstract: Myelin basic protein (MBP) plays an integral role in the structure and function of the myelin sheath. In humans and cattle, an 18.5-kDa isoform of MBP predominates and exists as a multitude of charge isomers resulting from extensive and varied post-translational modifications. We have purified the least modified isomer (named C1) of the 18.5-kDa isoform of MBP from fresh bovine brain and imaged this protein as negatively stained single particles adsorbed to a lipid monolayer. Under these conditions, MBP/C1 presented diverse projections whose relative orientations were determined using an iterative quaternion-assisted angular reconstitution scheme. In different buffers, one with a low salt and the other with a high salt concentration, the conformation of the protein was slightly different. In low salt buffer, the three-dimensional reconstruction, solved to a resolution of 4 nm, had an overall "C" shape of outer radius 5.5 nm, inner radius 3 nm, overall circumference 15 nm, and height 4.7 nm. The three-dimensional reconstruction of the protein in high salt buffer, solved to a resolution of 2.8 nm, was essentially the same in terms of overall dimensions but had a somewhat more compact architecture. These results are the first structures achieved directly for this unusual macromolecule, which plays a key role in the development of multiple sclerosis.
authors.affiliation: Department of Molecular Biology and Genetics, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: D R
authors.initials: DR
authors.lastname: Beniac
authors.forename: M D
authors.initials: MD
authors.lastname: Luckevich
authors.forename: G J
authors.initials: GJ
authors.lastname: Czarnota
authors.forename: T A
authors.initials: TA
authors.lastname: Tompkins
authors.forename: R A
authors.initials: RA
authors.lastname: Ridsdale
authors.forename: F P
authors.initials: FP
authors.lastname: Ottensmeyer
authors.forename: M A
authors.initials: MA
authors.lastname: Moscarello
authors.forename: G
authors.initials: G
authors.lastname: Harauz
mesh_terms: D000818:Animals; D002417:Cattle; D008854:Microscopy, Electron; D008958:Models, Molecular; D004676:Myelin Basic Protein / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D004676:Myelin Basic Protein