Titin
Titin , also known as connectin, is a protein that in humans is encoded by the "TTN" gene. Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring which 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 line to the M line in the sarcomere. The protein contributes to force transmission at the Z line 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 muscle (e.g., 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).
Q8054
protein
Concept
Q7187
gene
Concept
Q175821
µm
Concept
Q102836
spring
Concept
Q1048687
muscle
Concept
Q898273
protein domain
Concept
Q172847
peptide
Concept
Q273186
unfold
Concept
Q847556
refold
Concept
Q191817
striated muscle tissue
Concept
None
Z line
UNK
None
M line
UNK
Q1337087
sarcomere
Concept
None
I band
UNK
Q271727
myosin
Concept
Q185269
actin
Concept
Q8066
amino acid
Concept
Q21114084
splice isoform
UNK
Q8054
protein
Concept
Q373027
exon
Concept
Q74314
Titin
Concept
Q74314
Titin
Concept
Q74314
Titin
Concept
Q74314
Titin
Concept
+1^^http://www.w3.org/2001/XMLSchema#decimal
1
NUMBER
+0.5^^http://www.w3.org/2001/XMLSchema#decimal
0.5
NUMBER
+27.000^^http://www.w3.org/2001/XMLSchema#decimal
27,000
NUMBER
+35.000^^http://www.w3.org/2001/XMLSchema#decimal
35,000
NUMBER
+363^^http://www.w3.org/2001/XMLSchema#decimal
363
NUMBER
+17.106^^http://www.w3.org/2001/XMLSchema#decimal
17,106
NUMBER
instance of
instance of
encodes
part of