Protein domain

Protein domain is a part of a 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 domains. One domain may appear in a variety of different proteins. Molecular evolution uses protein domains as building blocks and these may be recombined in different arrangements to create proteins with different functions. In general, domains vary in length from between about 25 amino acids up to 500 amino acids in length. The shortest domains, such as zinc fingers, are stabilized by metal ions or disulfide bridges. Longer domains, like kinase domains, are often composed of several well-defined secondary structure elements. Domains in protein function and evolution are a fundamental concept in molecular biology.

Structure and Function

Protein domains are parts of a protein that can function and evolve independently of the rest of the protein chain. They are compact, three-dimensional structures that are often independently stable and folded. Domains can have specific functions, such as DNA-binding or enzyme activity, and they can also serve as interfaces for protein-protein interaction.

Evolution

Protein domains serve as the building blocks of molecular evolution. They can be recombined in different arrangements to create proteins with new functions. This is often seen in the evolution of multi-domain proteins, where domains with different functions are brought together to create a protein with a new and complex function.

Classification

Protein domains are classified into families based on sequence and structural similarity. The most widely used protein domain classification databases are Pfam and SCOP. Pfam classifies protein domains into families based on sequence similarity, while SCOP classifies domains based on structural similarity.

See Also

• Protein structure
• Protein folding
• Protein-protein interaction
• Protein family
• Protein subunit

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