title: A structural model for the GroEL chaperonin.
abstract: Individual particle analysis of end views from negatively stained specimens of purified GroEL from Escherichia coli showed the presence of two different particle populations, those with a six-fold symmetry and those with a seven-fold symmetry, when studied at pH 7.7 and 5.0. Image processing of particles from frozen-hydrated specimens revealed at both pH values a homogeneous population of particles with a strong seven-fold symmetry component and an average image with seven asymmetric units. Biochemical analysis of purified GroEL showed unequivocally the presence of a single polypeptide with the N-terminal sequence identical to that of GroEL. These results are compatible with a structural model of GroEL as an asymmetric aggregate built up by two rings of seven-fold and six-fold symmetries, respectively.
authors.affiliation: Centro de Biología Molecular, Universidad Autónoma de Madrid, Cantoblanco, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Marco
authors.forename: J M
authors.initials: JM
authors.lastname: Valpuesta
authors.forename: G
authors.initials: G
authors.lastname: Rivas
authors.forename: G
authors.initials: G
authors.lastname: Andrés
authors.forename: C
authors.initials: C
authors.lastname: San Martín
authors.forename: J L
authors.initials: JL
authors.lastname: Carrascosa
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D018834:Chaperonin 60; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; D018834:Chaperonin 60; D006360:Heat-Shock Proteins