[6][7] The protein, which is over 1 μm in length,[8] functions as a molecular spring that is responsible for the passive elasticity of muscle.

[16] In 1977, Koscak Maruyama and coworkers isolated an elastic protein from muscle fiber that they called connectin.

[17] Two years later, Kuan Wang and coworkers identified a doublet band on electrophoresis gel corresponding to a high molecular weight, elastic protein that they named titin.

[7] Five years later, Labeit and Bernhard Kolmerer determined the cDNA sequence of human cardiac titin.

[15][19] The human gene encoding for titin is located on the long arm of chromosome 2 and contains 363 exons, which together code for 38,138 amino acid residues (4200 kDa).

[20] A number of titin isoforms are produced in different striated muscle tissues as a result of alternative splicing.

[31] The elasticity of the PEVK region has both entropic and enthalpic contributions and is characterized by a polymer persistence length and a stretch modulus.

The difference between low-and high- stretch elasticity is due to electrostatic stiffening and hydrophobic effects.

Throughout evolution, titin mechanical strength appears to decrease through the loss of disulfide bonds as the organism becomes heavier.

[35] Titin A-band has homologs in invertebrates, such as twitchin (unc-22) and projectin, which also contain Ig and FNIII repeats and a protein kinase domain.

[28] Drosophila projectin, officially known as bent (bt), is associated with lethality by failing to escape the egg in some mutations as well as dominant changes in wing angles.

It is homologous to vertebrate titin I-band and contains Ig PEVK domains, the many repeats being a hot target for splicing.

Titin also contains binding sites for muscle-associated proteins so it serves as an adhesion template for the assembly of contractile machinery in muscle cells.

[45] Titin interacts with many sarcomeric proteins including:[15] Mutations anywhere within the unusually long sequence of this gene can cause premature stop codons or other defects.

[51] Further research also suggests that no genetically linked form of any dystrophy or myopathy can be safely excluded from being caused by a mutation on the TTN gene.