title: Annular arrangement and collaborative actions of four domains of protein-disulfide isomerase: a small angle X-ray scattering study in solution.
abstract: We presented for the first time a small angle x-ray scattering study of intact protein-disulfide isomerase (PDI) in solution. The restored model revealed that PDI is a short and roughly elliptical cylinder with a molecular mass of 69 kDa and dimensions of 105 x 65 x 40 A, and the four thioredoxin-fold domains in the order a-b-b'-a' are arranged in an annular fashion. Atomic force microscope imaging also supported the finding that PDI appears as an approximately flat elliptical cylinder. A PDI species with apparent molecular mass of 116 kDa measured by using size-exclusion chromatography, previously assumed to be a dimer, was determined to exist mainly as a monomer by using analytical ultracentrifugation. The C-terminal fragment 441-491 contributed to the anomalous molecular mass determination of PDI by size-exclusion chromatography. The annular model of PDI accounted for the cooperative properties of the four domains in both the isomerase and chaperone functions of PDI.
authors.affiliation: National Laboratory of Biomacromolecules, Chinese Academy of Sciences, Beijing, China.
authors.forename: Sheng-jian
authors.initials: SJ
authors.lastname: Li
authors.forename: Xin-guo
authors.initials: XG
authors.lastname: Hong
authors.forename: Yuan-yuan
authors.initials: YY
authors.lastname: Shi
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.forename: Chih-chen
authors.initials: CC
authors.lastname: Wang
mesh_terms: D018360:Crystallography, X-Ray; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism*; D019704:Protein Disulfide-Isomerases / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012542:Scattering, Radiation; D012996:Solutions; D014965:X-Rays
chemical_list: D018832:Molecular Chaperones; D012996:Solutions; D019704:Protein Disulfide-Isomerases