title: A novel, highly stable fold of the immunoglobulin binding domain of streptococcal protein G.
abstract: The high-resolution three-dimensional structure of a single immunoglobulin binding domain (B1, which comprises 56 residues including the NH2-terminal Met) of protein G from group G Streptococcus has been determined in solution by nuclear magnetic resonance spectroscopy on the basis of 1058 experimental restraints. The average atomic root-mean-square distribution about the mean coordinate positions is 0.27 angstrom (A) for the backbone atoms, 0.65 A for all atoms, and 0.39 A for atoms excluding disordered surface side chains. The structure has no disulfide bridges and is composed of a four-stranded beta sheet, on top of which lies a long helix. The central two strands (beta 1 and beta 4), comprising the NH2- and COOH-termini, are parallel, and the outer two strands (beta 2 and beta 3) are connected by the helix in a +3x crossover. This novel topology (-1, +3x, -1), coupled with an extensive hydrogen-bonding network and a tightly packed and buried hydrophobic core, is probably responsible for the extreme thermal stability of this small domain (reversible melting at 87 degrees C).
authors.affiliation: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
authors.forename: A M
authors.initials: AM
authors.lastname: Gronenborn
authors.forename: D R
authors.initials: DR
authors.lastname: Filpula
authors.forename: N Z
authors.initials: NZ
authors.lastname: Essig
authors.forename: A
authors.initials: A
authors.lastname: Achari
authors.forename: M
authors.initials: M
authors.lastname: Whitlow
authors.forename: P T
authors.initials: PT
authors.lastname: Wingfield
authors.forename: G M
authors.initials: GM
authors.lastname: Clore
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000276:immunology; D001665:Binding Sites; D002151:Calorimetry; D006860:Hydrogen Bonding; D007074:Immunoglobulin G; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus; D007074:Immunoglobulin G