A novel, highly stable fold of the immunoglobulin binding domain of streptococcal protein G

Science. 1991 Aug 9;253(5020):657-61. doi: 10.1126/science.1871600.


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).

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / immunology
  • Binding Sites
  • Calorimetry
  • Hydrogen Bonding
  • Immunoglobulin G*
  • Magnetic Resonance Spectroscopy / methods
  • Models, Molecular
  • Protein Conformation


  • Bacterial Proteins
  • IgG Fc-binding protein, Streptococcus
  • Immunoglobulin G