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Sliding filament model of muscle contraction. (Titin labeled at upper right.)
Symbol TTN
Entrez 7273
HUGO 12403
OMIM 188840
RefSeq NM_133378
UniProt Q8WZ42
Other data
Locus Chr. 2 q31

Titin, also known as connectin[1] (UniProt name: Q10466_HUMAN; accession number: Q10466), is a protein that is important in the contraction of striated muscle tissues.


Titin is the largest known protein, consisting of 26,926 amino acids. The molecular weight of the mature protein is approximately 2,993,451.39 Da, and it has a theoretical pI of 6.01[2] The protein's empirical chemical formula is C132983H211861N36149O40883S693. It has a theoretical instability index (II) of 39.69, indicating that it would be stable in a test tube. The protein's in vivo half-life, the time it takes for half of the amount of protein in a cell to disappear after its synthesis in the cell, is predicted to be approximately 30 hours (in mammalian reticulocytes).[3]

Linguistic significance

As the largest known protein, titin has the longest full chemical name. The full chemical name, containing 189,819 letters, is sometimes stated to be the longest word in the English language.


  1. ^ Online 'Mendelian Inheritance in Man' (OMIM) 188840
  2. ^ ExPASy-calculated pI for titin. Retrieved on 2007-08-26.
  3. ^ Swiss-Prot Protein knowledgebase, main entry. Retrieved on 2006-05-04.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Titin". A list of authors is available in Wikipedia.
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