Titins: Giant Proteins in Charge of Muscle Ultrastructure and Elasticity

  title={Titins: Giant Proteins in Charge of Muscle Ultrastructure and Elasticity},
  author={Siegfried Labeit and Bernhard Kolmerer},
  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
Titin-thin filament interaction and potential role in muscle function.
  • J. Jin
  • Biology
    Advances in experimental medicine and biology
  • 2000
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
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
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.
Mechanical properties of titin isoforms.
It is proposed that, along the physiological SL range, the long PEVK segment found in N2BA titins results in a low PEVK fractional extension and that this underlies the lower passive tensions of N2 BA-expressing cow myocytes.
Palindromic assembly of the giant muscle protein titin in the sarcomeric Z-disk
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.
How titin regulates passive and active properties of striated muscle during normal muscle function and during disease is discussed.


A physiological role for titin and nebulin in skeletal muscle
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.
Towards a molecular understanding of titin.
It is concluded that A‐band titin is likely to be involved in the ordered assembly of the vertebrate thick filament.
Regulation of skeletal muscle stiffness and elasticity by titin isoforms: a test of the segmental extension model of resting tension.
Immunoelectron microscopic studies of an epitope in the extensible segment of titin revealed a transition in the elastic behavior of the titin filaments near the yield point sarcomere length of these muscles, providing direct evidence of tit in's involvement in the genesis of resting tension.
Phosphorylation of KSP motifs in the C‐terminal region of titin in differentiating myoblasts.
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.
Structure of A-segments from frog and rabbit skeletal muscle.
  • R. Craig
  • Biology
    Journal of molecular biology
  • 1977