Cellulosomes are cell-bound multienzyme complexes secreted by anaerobic bacteria that play a crucial role in carbon turnover by degrading plant cell walls to simple sugars. Integration of cellulosomal components occursviahighly ordered protein–protein interactions between cohesin modules located in a molecular scaffold and dockerin modules found in cellulosomal enzymes.Acetivibrio cellulolyticuspossesses a complex cellulosome arrangement which is organized by a primary enzyme-binding scaffoldin (ScaA), two anchoring scaffoldins (ScaC and ScaD) and an unusual adaptor scaffoldin (ScaB). A dockerin from a family 5 glycoside hydrolase (GH5), which was engineered to inactivate one of the two putative cohesin-binding interfaces, complexed with one of the ScaA cohesins fromA. cellulolyticushas been purified and crystallized, and data were processed to a resolution of 1.57 Å in the orthorhombic space groupP2₁2₁2₁.