  Cellulosomes are complex multi-enzyme machineries which efficiently degrade
plant cell-wall polysaccharides. The multiple domains of the cellulosome
proteins are often tethered together by intrinsically disordered regions. The
properties and functions of these disordered linkers are not well understood.
In this work, we study endoglucanase Cel8A, which is a relevant enzymatic
component of the cellulosomes of Clostridium thermocellum. We use both all-atom
and coarse-grained simulations to investigate how the equilibrium conformations
of the catalytic domain of Cel8A are affected by the disordered linker at its C
terminus. We find that when the endoglucanase is bound to its substrate, the
effective stiffness of the linker can influence the distances between groups of
amino-acid residues throughout the entire enzymatic domain. In particular,
variations in the linker stiffness can lead to small changes in the geometry of
the active-site cleft. We suggest that such geometrical changes may, in turn,
have an effect on the catalytic activity of the enzyme.
