Titin

  • OMIM: 188 840
  • MGI: 98864

Titin (also connectin ) is an approximately 3.6 megadalton heavy elastic protein that is composed into filaments (protein filaments ). It consists of over 30,000 amino acids and contains 320 protein domains, making it the largest known human protein. It is a part of the sarcomere, the smallest functional unit of striated muscle. The role of titin in the sarcomere, the myosin heads to center between the actin filaments and reset the contractile apparatus after stretching.

The Titinfilament mechanically coupled together with the actin filament on alpha actinin with the Z- plate. This binding is relatively weak and easily adjustable, a necessary condition for the unimpeded contraction process. In addition, it binds in the Z-disk to Telethonin (T- cap). In the area of the A - strip is attached with his stiff end to the myosin filament and binds to the calcium-dependent protease calpain.

In the region of the long strip - I polypeptide is elastic and can be stretched. The structure of the titin differs in skeletal and cardiac muscles, so that the lower extensibility of the cardiac sarcomere can be explained.

At the muscle contraction the Titinfilament is not involved, it provides the flexibility and stability of the muscle and determines the speed of contraction to a significant extent with. In addition, titin is responsible for the resting tension of the muscle and is therefore often cited in discussions about sense or nonsense of stretching.

Trivia

As the longest known protein, the protein titin has according to the rules of the IUPAC also the longest systematic name of a chemical compound. In this generic name is the concatenation of the amino acids named in the correct order, that is, in the primary structure of the protein. The systematic name of titin begins with " methionyl .... " and ends with " ... isoleucine ." It is controversial whether such generic names are regular words. The reading of the generic name takes several hours, the word consists of approximately 190,000 letters.

Protein isoform Human Genome Organisation Mouse Genome Informatics Euteleostomi Entrez Ensembl UniProt National Center for Biotechnology Information
200112
de