Titin

TTN
Available structures
PDB	Ortholog search: A2ASS6%20or%20Q8WZ42%20or%20 A2ASS6%20or%20H0Y4J7 PDBe A2ASS6,Q8WZ42, A2ASS6,H0Y4J7 RCSB
List of PDB id codes
	4UOW, 1BPV, 1G1C, 1NCT, 1NCU, 1TIT, 1TIU, 1TKI, 1TNM, 1TNN, 1WAA, 1YA5, 2A38, 2BK8, 2F8V, 2ILL, 2J8H, 2J8O, 2NZI, 2RQ8, 2WP3, 2WWK, 2WWM, 2Y9R, 3KNB, 3LCY, 3LPW, 3PUC, 3Q5O, 3QP3, 4C4K, 4JNW, 4O00, 4QEG, 5BS0
Identifiers
Aliases	TTN, CMD1G, CMH9, CMPD4, EOMFC, HMERF, LGMD2J, MYLK5, TMD, titin, SALMY, LGMDR10
External IDs	OMIM: 188840; MGI: 98864; HomoloGene: 130650; GeneCards: TTN; OMA:TTN - orthologs
EC number	2.7.11.1
Gene location (Human)
Chr.	Chromosome 2 (human)
End	178,830,802 bp
Gene location (Mouse)
Chr.	Chromosome 2 (mouse)
End	76,982,547 bp
RNA expression pattern
	Top expressed in
	glutes; ; Skeletal muscle tissue of biceps brachii; ; triceps brachii muscle; ; Skeletal muscle tissue of rectus abdominis; ; right ventricle; ; thoracic diaphragm; ; body of tongue; ; vastus lateralis muscle; ; deltoid muscle; ; myocardium of left ventricle;
	Top expressed in
	vastus lateralis muscle; ; digastric muscle; ; triceps brachii muscle; ; sternocleidomastoid muscle; ; knee joint; ; body of femur; ; temporal muscle; ; atrium; ; intercostal muscle; ; medial head of gastrocnemius muscle;
	More reference expression data
	More reference expression data
Gene ontology
Molecular function	transferase activity; nucleotide binding; calcium ion binding; protein kinase activity; actinin binding; muscle alpha-actinin binding; structural molecule activity conferring elasticity; metal ion binding; telethonin binding; protease binding; protein self-association; actin filament binding; protein serine/threonine kinase activity; kinase activity; protein binding; identical protein binding; enzyme binding; protein tyrosine kinase activity; structural constituent of muscle; ATP binding; protein kinase binding; calmodulin binding; structural constituent of cytoskeleton; ankyrin binding;
Cellular component	cytoplasm; cytosol; I band; striated muscle thin filament; condensed nuclear chromosome; extracellular region; Z discdkac; muscle myosin complex; extracellular exosome; nucleus; M band; sarcomere; A band; myofibril;
Biological process	sarcomerogenesis; muscle contraction; mitotic chromosome condensation; cardiac muscle contraction; phosphorylation; cardiac muscle hypertrophy; platelet degranulation; cardiac muscle tissue morphogenesis; skeletal muscle thin filament assembly; detection of muscle stretch; response to calcium ion; cardiac myofibril assembly; protein phosphorylation; muscle filament sliding; regulation of protein kinase activity; regulation of catalytic activity; sarcomere organization; skeletal muscle myosin thick filament assembly; striated muscle contraction; peptidyl-tyrosine phosphorylation; positive regulation of gene expression; protein kinase A signaling; positive regulation of protein secretion; somitogenesis; ventricular system development; in utero embryonic development; heart morphogenesis; striated muscle cell development; heart growth; adult heart development; forward locomotion; heart development; regulation of relaxation of cardiac muscle; actin filament organization; striated muscle myosin thick filament assembly;
	Sources:Amigo / QuickGO
Orthologs
	7273
	22138
	ENSG00000155657
	ENSMUSG00000051747
	Q8WZ42
	Q8WZ42
NM_001256850; NM_001267550; NM_003319; NM_133378; NM_133379;
	NM_133432; NM_133437
	NM_011652; NM_028004
NP_001243779; NP_001254479; NP_003310; NP_596869; NP_596870;
	NP_597676; NP_597681; NP_035782; NP_082280; NP_001372637
NP_001243779; NP_001254479; NP_003310; NP_596869; NP_596870;
	NP_597676; NP_597681; NP_035782; NP_082280; NP_001372637
	Wikidata
View/Edit Human	View/Edit Mouse

Titin (/ˈtaɪtɪn/; also called connectin) is a protein that in humans is encoded by the TTN gene. The protein, which is over 1 μm in length, functions as a molecular spring that is responsible for the passive elasticity of muscle. It comprises 244 individually folded protein domains connected by unstructured peptide sequences. These domains unfold when the protein is stretched and refold when the tension is removed.

Titin is important in the contraction of striated muscle tissues. It connects the Z disc to the M line in the sarcomere. The protein contributes to force transmission at the Z disc and resting tension in the I band region. It limits the range of motion of the sarcomere in tension, thus contributing to the passive stiffness of muscle. Variations in the sequence of titin between different types of striated muscle (cardiac or skeletal) have been correlated with differences in the mechanical properties of these muscles.

Titin is the third most abundant protein in muscle (after myosin and actin), and an adult human contains approximately 0.5 kg of titin. With its length of ~27,000 to ~35,000 amino acids (depending on the splice isoform), titin is the largest known protein. Furthermore, the gene for titin contains the largest number of exons (363) discovered in any single gene, as well as the longest single exon (17,106 bp).