Dockerin is a protein domain

Protein domain

A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...

 found in the Cellulosome cellular structure. It is part of endoglucanase enzymes. The dockerin's binding partner is the cohesin

Cohesin domain

In molecular biology, the cohesin domain is a protein domain. It interacts with a complementary domain, termed the dockerin domain. The cohesin-dockerin interaction is the crucial interaction for complex formation in the cellulosome....

 domain. This interaction is essential to the construction of the Cellulosome complex (also known as a Scaffoldin). The Dockerin domain has two in-tandem repeats of a non-EF hand

EF hand

The EF hand is a helix-loop-helix structural domain found in a large family of calcium-binding proteins. The EF-hand motif contains a helix-loop-helix topology, much like the spread thumb and forefinger of the human hand, in which the Ca2+ ions are coordinated by ligands within the loop...

 calcium binding motif. Each motif is characterized by a loop-helix structure. The three dimensional structure of dockerin has been determined in solution, as well as in complex with Cohesin.

There are three types of Dockerin domains: I, II and III which bind to Cohesin Type I, Cohesin Type II and Cohesin Type III respectively. A type I dockerin domain is 65-70 residue

Residue (chemistry)

In chemistry, residue is the material remaining after a distillation or an evaporation, or to a portion of a larger molecule, such as a methyl group. It may also refer to the undesired byproducts of a reaction....

s long. The binding specificity of Type I interaction was well studied by structural and mutagenesis

Mutagenesis

Mutagenesis is a process by which the genetic information of an organism is changed in a stable manner, resulting in a mutation. It may occur spontaneously in nature, or as a result of exposure to mutagens. It can also be achieved experimentally using laboratory procedures...

studies. Type II interaction is less well characterized.