Marlene Duarte, Aldino Viegas, Victor D. Alves, José A.M. Prates, Luís M.A. Ferreira, Shabir Najmudin, Eurico J. Cabrita, Ana Luisa Carvalho, Carlos MGA Fontes, and Pedro Bule
Cohesin-dockerin binding mode in Bacteroides cellulosolvens reflects the size and complexity of its cellulosome
The Cellulosome is one of nature’s most intricate macromolecular protein complexes. Cellulosomes centralize the cellulolytic efforts of many anaerobic microorganisms through the promotion of enzyme synergy and protein stability. The assembly of a multitude of carbohydrate processing enzymes into a macromolecular multi-protein structure results from the interaction of enzyme-borne dockerin modules with repeated cohesin modules present in non-catalytic scaffold proteins, termed scaffoldins. Cohesin-dockerin (Coh-Doc) modules are typically classified into different types, depending on structural conformation and cellulosome role. Thus, type I Coh-Doc complexes are usually responsible for enzyme integration into the cellulosome, while type II Coh-Doc complexes articulate the interaction of cellulosome with the bacterial wall. In contrast to other known cellulosomes, Bacteroides cellulosolvens cohesin types are reversed for all scaffoldins, i.e., the type II cohesins are located on the enzyme-integrating primary scaffoldin, whereas the type I cohesins are located on the anchoring scaffoldins. It has been previously shown that type I B. cellulosolvens interactions possess a dual-binding mode that adds flexibility to scaffoldin assembly. Here is reported the structural mechanism of enzyme recruitment into B. cellulosolvens cellulosome and the identification of the molecular determinants of its type II cohesin-dockerin interactions.
The results indicate that, unlike other type II complexes, these possess a dual binding mode of interaction, similarly to type I.
Therefore, the plasticity of dual-binding mode interactions seems to play a pivotal role in the assembly of B. cellulosolvens cellulosome, which is consistent with its unmatched complexity and size.
Read more:
Comments