Crucial roles of single residues in binding affinity, specificity and promiscuity in the cellulosomal cohesin-dockerin interface [Molecular Biophysics]

April 1st, 2015 by Slutzki, M., Reshef, D., Barak, Y., Haimovitz, R., Rotem-Bamberger, S., Lamed, R., Bayer, E. A., Schueler-Furman, O.

Interactions between cohesin and dockerin modules play a crucial role in the assembly of multi-enzyme cellulosome complexes. While intra-species cohesin and dockerin modules bind in general with high affinity but indiscriminately, cross-species binding is rare. Here, we combined ELISA-based experiments with Rosetta-based computational design to evaluate the contribution of distinct residues at the Clostridium thermocellum (Ct) cohesin- dockerin interface to binding affinity, specificity and promiscuity. We found that single mutations can show distinct and significant effects on binding affinity and specificity. In particular, mutations at cohesin position N37 show dramatic variability in their effect on dockerin binding affinity and specificity: The N37A mutant binds promiscuously both to cognate (Ct) as well as to non-cognate C. cellulolyticum (Cc) dockerin. N37L in turn switches binding specificity: compared to the wild-type Ct cohesin, this mutant shows significantly increased preference for Cc dockerin, combined with strongly reduced binding to its cognate Ct dockerin. The observation that a single mutation can overcome the naturally observed specificity barrier provides insights into the evolutionary dynamics of this system that allows rapid modulation of binding specificity within a high-affinity background.
  • Posted in Journal of Biological Chemistry, Publications
  • Comments Off on Crucial roles of single residues in binding affinity, specificity and promiscuity in the cellulosomal cohesin-dockerin interface [Molecular Biophysics]