Titin (pron.: /ˈtaɪtɪn/), also
known as connectin, is a protein that
in humans is encoded by the TTN gene.
Titin is a giant protein that
functions as a molecular spring which is responsible for the passive elasticity
of muscle. It is composed of 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) has been correlated with differences in the mechanical
properties of these muscles.
With its length of ~27,000 to
~33,000 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.
It has 189819
characters long of its chemical name (Longest till now) and takes approximately
3.5 hours to read it for a normal reader.
Structure :
