Cell-surface attachment of bacterial cellulosomes revealed by UCIBIO researchers

Benedita Pinheiro, Ana Luísa Carvalho and Maria João Romão, researchers from UCIBIO at FCT-NOVA, in a long lasting collaboration with the Faculty of Veterinary Medicine (Lisbon University), contribute to the elucidation of the unique molecular mechanisms used by anaerobic bacteria for cellular attachment of cellulosomes. Cellulosomes are one of Nature’s most intricate multi-enzyme complexes dedicated to degrade cellulosic biomass to simpler sugars. “Knowledge about this very efficient nano-machine has enormous interest not only to produce bioethanol, but also for the construction of other dynamic protein assemblies”, explains Ana Luísa Carvalho, researcher in the Macromolecular Crystallography Lab at UCIBIO, in FCT-NOVA. The research work that reveals how this assembly attaches to the bacterial cell walls from Clostridium thermocellum and Acetivibrio cellulolyticus was recently published in Scientific Reports.

Attachment is achieved through dynamic interaction of cohesin and dockerin modules. The structures of five different cohesin-dockerin complexes (illustrated below), from the two bacteria, were solved by X-ray Crystallography to reveal the functional complexity of cellulosome recruitment to the cell envelope. “In contrast to a previously suggested “static” model, the data support the hypothesis that binding of large cellulosomal complexes to the bacterial surface is mediated by a dual-binding mode that, nonetheless, assumes a diversity of mechanisms in different bacteria”, explains Ana Luísa Carvalho.

Ribbon representation of selected cohesin-dockerin complexes.
The structure of CtCohScaC2-XDocCipB complex (Panel A) is overlaid with the structure of CtCohScaF-XDocScaA (Panel B). 


Modular organization of C. thermocellum and A. cellulolyticus cellulosomes



Diverse specificity of cellulosome attachment to the bacterial cell surface
Scientific Reports 6: 38292, 2016 | doi:10.1038/srep38292
Joana L. A. Brás, Benedita A. Pinheiro, Kate Cameron, Fiona Cuskin, Aldino Viegas, Shabir Najmudin, Pedro Bule, Virginia M. R. Pires, Maria João Romão, Edward A. Bayer, Holly L. Spencer, Steven Smith, Harry J. Gilbert, Victor D. Alves, Ana Luísa Carvalho & Carlos M. G. A. Fontes