Titins: Giant Proteins in Charge of Muscle Ultrastructure and Elasticity

@article{Labeit1995TitinsGP,
  title={Titins: Giant Proteins in Charge of Muscle Ultrastructure and Elasticity},
  author={Siegfried Labeit and Bernhard Kolmerer},
  journal={Science},
  year={1995},
  volume={270},
  pages={293 - 296}
}
In addition to thick and thin filaments, vertebrate striated muscle contains a third filament system formed by the giant protein titin. Single titin molecules extend from Z discs to M lines and are longer than 1 micrometer. The titin filament contributes to muscle assembly and resting tension, but more details are not known because of the large size of the protein. The complete complementary DNA sequence of human cardiac titin was determined. The 82-kilobase complementary DNA predicts a 3… 

The giant protein titin. Emerging roles in physiology and pathophysiology.

Titin is a giant protein of vertebrate striated muscles (M(r), > or = 3000 kD). Its molecules are of filamentous shape and span from the Z disk to the M line, thereby forming a third filament system

Stretching molecular springs: elasticity of titin filaments in vertebrate striated muscle.

  • W. Linke
  • Biology
    Histology and histopathology
  • 2000
TLDR
Examination of N2-B titin extensibility revealed that this isoform extends by recruiting three distinct elastic elements: poly-Ig regions and the PEVK domain at lower stretch and, in addition, a unique 572-residue sequence insertion at higher physiological stretch.

Titin-thin filament interaction and potential role in muscle function.

  • J. Jin
  • Biology
    Advances in experimental medicine and biology
  • 2000
TLDR
It is speculated that the Ca(2+)-mediated thin filament regulation may coordinate the function of titin during muscle contraction and relaxation, supported by an epitope similarity between the actin-binding site of caldesmon and the immunoglobulin-like module of Titin.

The giant protein titin regulates the length of the striated muscle thick filament

TLDR
It is shown that the length of thick filaments is defined by titin, and that alterations in titin length affect force generation and lead to dilated cardiomyopathy in mice.

Role of titin in vertebrate striated muscle.

  • L. TskhovrebovaJ. Trinick
  • Biology
    Philosophical transactions of the Royal Society of London. Series B, Biological sciences
  • 2002
TLDR
It is suggested that, due to the limited conformational space, elongation and compression of the molecule within the sarcomere occur in a more ordered way or with higher viscosity and higher forces than are observed in solution studies of the isolated protein.

Elasticity and unfolding of single molecules of the giant muscle protein titin

TLDR
Mechanical experiments on single molecules of titin are done to determine their visco-elastic properties, showing that there are two main sources of elasticity: one deriving from the entropy of straightening the molecule; the other consistent with extension of the polypeptide chain in the PEVK region.

Evidence for the oligomeric state of 'elastic' titin in muscle sarcomeres.

Palindromic assembly of the giant muscle protein titin in the sarcomeric Z-disk

TLDR
This work shows, using X-ray crystallography, how the amino terminus of the longest filament component, the giant muscle protein titin, is assembled into an antiparallel (2:1) sandwich complex by the Z-disk ligand telethonin.

Physiological functions of the giant elastic protein titin in mammalian striated muscle.

TLDR
How titin regulates passive and active properties of striated muscle during normal muscle function and during disease is discussed.
...

References

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TLDR
The ability of single skinned muscle cells to generate both passive tension in response to stretch and active tension in Response to calcium is greatly reduced after low doses of ionizing radiation, accompanied by axial misalignment of thick filaments.

Titin folding energy and elasticity

TLDR
In the present experiments, equilibrium unfolding of titin from rabbit skeletal muscles was studied in vitro by fluorescence and circular dichroism spectroscopy, and the data suggest two unfolding transitions, both of which appear cooperative.

Towards a molecular understanding of titin.

TLDR
It is concluded that A‐band titin is likely to be involved in the ordered assembly of the vertebrate thick filament.

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TLDR
It is concluded that titin is a structurally conserved myofibrillar component of vertebrate and invertebrate striated muscles.

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TLDR
It is suggested that titin C‐terminal phosphorylation by SP‐specific kinases is regulated during differentiation, and that this may control the assembly of M‐line proteins into regular structures during myogenesis.