Protein disorder: conformational distribution of the flexible linker in a chimeric double cellulase

Biophys J. 2005 Apr;88(4):2823-32. doi: 10.1529/biophysj.104.050146. Epub 2005 Jan 14.


The structural properties of the linker peptide connecting the cellulose-binding module to the catalytic module in bimodular cellulases have been investigated by small-angle x-ray scattering. Since the linker and the cellulose-binding module are relatively small and cannot be readily detected separately, the conformation of the linker was studied by means of an artificial fusion protein, Cel6BA, in which an 88-residue linker connects the large catalytic modules of the cellulases Cel6A and Cel6B from Humicola insolens. Our data showed that Cel6BA is very elongated with a maximum dimension of 178 A, but could not be described by a single conformation. Modeling of a series of Cel6BA conformers with interdomain separations ranging between 10 A and 130 A showed that good Guinier and P(r) profile fits were obtained by a weighted average of the scattering curves of all the models where the linker follows a nonrandom distribution, with a preference for the more compact conformers. These structural properties are likely to be essential for the function of the linker as a molecular spring between the two functional modules. Small-angle x-ray scattering therefore provides a unique tool to quantitatively analyze the conformational disorder typical of proteins described as natively unfolded.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Ascomycota / metabolism
  • Biophysics / methods*
  • Catalytic Domain
  • Cellulase / chemistry*
  • Cellulose / chemistry
  • Hydrolysis
  • Models, Molecular
  • Models, Statistical
  • Molecular Conformation
  • Molecular Sequence Data
  • Protein Conformation
  • Protein Structure, Tertiary
  • Proteins / chemistry
  • Recombinant Fusion Proteins / chemistry
  • Scattering, Radiation
  • X-Rays


  • Proteins
  • Recombinant Fusion Proteins
  • Cellulose
  • Cellulase