Dockerin

Dockerin is a small protein module found in cellulosome-producing bacteria, such as certain Clostridium and Ruminococcus species. It functions as a docking unit that binds to cohesin modules on scaffoldin proteins, enabling the assembly of a multi-enzyme complex known as the cellulosome. This modular arrangement brings together carbohydrate-degrading enzymes in close proximity, enhancing the breakdown of plant cell wall polysaccharides.

Most dockerin domains are calcium-binding and about 60 amino acids in length. The interaction with cohesins is calcium-dependent and highly specific, which allows different dockerin modules to recognize particular cohesin types. In some organisms, multiple dockerin types enable selective binding to different scaffoldins, while others feature dual dockerins capable of engaging more than one cohesin category. The calcium dependency also stabilizes the dockerin fold necessary for cohesive binding.

Structurally, dockerins are compact domains that present a binding surface compatible with the cohesin groove. The precise assembly of dockerins and cohesins determines the composition and architecture of the cellulosome, influencing which enzymes are displayed and how effectively they degrade substrates such as cellulose and hemicellulose.

Biological significance and applications: the dockerin-cohesin system is central to the efficiency of plant biomass degradation in anaerobic microbes. It has attracted interest for basic research into protein-protein interactions and for biotechnological applications, including the design of engineered cellulosomes for improved biomass conversion and methods for immobilizing enzymes on designed scaffolds. See also cellulosome, cohesin, scaffoldin.