title: Protein disorder: conformational distribution of the flexible linker in a chimeric double cellulase.
abstract: 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.
authors.affiliation: Novozymes A/S, Bagsvaerd, Denmark.
authors.forename: Ingemar
authors.initials: I
authors.lastname: von Ossowski
authors.forename: Julian T
authors.initials: JT
authors.lastname: Eaton
authors.forename: Mirjam
authors.initials: M
authors.lastname: Czjzek
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Perkins
authors.forename: Torben P
authors.initials: TP
authors.lastname: Frandsen
authors.forename: Martin
authors.initials: M
authors.lastname: Schülein
authors.forename: Pierre
authors.initials: P
authors.lastname: Panine
authors.forename: Bernard
authors.initials: B
authors.lastname: Henrissat
authors.forename: Veronique
authors.initials: V
authors.lastname: Receveur-Bréchot
mesh_terms: D000595:Amino Acid Sequence; D001203:Ascomycota / Q000378:metabolism; D001703:Biophysics / Q000379:methods*; D020134:Catalytic Domain; D002480:Cellulase / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry; D006868:Hydrolysis; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D014965:X-Rays
chemical_list: D011506:Proteins; D011993:Recombinant Fusion Proteins; D002482:Cellulose; D002480:Cellulase