Protein disorder: conformational distribution of the flexible linker in a chimeric double cellulase.
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.
von Ossowski
Ingemar
I
Novozymes A/S, Bagsvaerd, Denmark.
Eaton
Julian T
JT
Czjzek
Mirjam
M
Perkins
Stephen J
SJ
Frandsen
Torben P
TP
Schülein
Martin
M
Panine
Pierre
P
Henrissat
Bernard
B
Receveur-Bréchot
Veronique
V
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
D011506:Proteins; D011993:Recombinant Fusion Proteins; D002482:Cellulose; D002480:Cellulase