title: The secondary structure of protein G', a robust molecule.
abstract: The secondary structure of recombinant streptococcal Protein G' was predicted and compared with spectropolarimetric data. The predicted secondary structure consisted of 37 +/- 4% alpha-helix and 30 +/- 5% beta-sheet, whereas the values obtained from c.d. data were 29 +/- 2% alpha-helix and 41 +/- 3% beta-sheet. An alpha-helix-beta-sheet/turn-alpha-helix motif is conjectured to comprise the Fc-binding unit. The c.d. spectra in the near u.v. and far u.v. show that the Protein G' molecule is stable to heating at 100 degrees C and to extremes of pH (pH 1.5 to 11.0). The protein retained biological activity at these extremes. The molecule uncoils above pH 11.5 in a time-dependent fashion. Unfolding of the molecule in guanidinium chloride was monitored by c.d. and fluorescence emission; 3 M-guanidinium chloride was required to unfold the protein by 50%. The protein was completely unfolded in 5.5 M-guanidinium chloride and fully refolded with restoration of activity after removal of guanidinium chloride.
authors.affiliation: Division of Biotechnology, P.H.L.S. Centre for Applied Microbiology and Research, Porton Down, Salisbury, Wilts, U.K.
authors.forename: C R
authors.initials: CR
authors.lastname: Goward
authors.forename: L I
authors.initials: LI
authors.lastname: Irons
authors.forename: J P
authors.initials: JP
authors.lastname: Murphy
authors.forename: T
authors.initials: T
authors.lastname: Atkinson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002942:Circular Dichroism; D003001:Cloning, Molecular; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D013291:Streptococcus / Q000235:genetics; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D006146:Guanidines; C034284:IgG Fc-binding protein, Streptococcus; D011994:Recombinant Proteins; D019791:Guanidine