Titine (protein)

The titine or connectine is a elastic Protéine implied in the control of the assembly of the sarcomeric Protéine S and which controls the elasticity of the Sarcomère. In the Muscle, it is related to the thick filaments (of Myosine), and extends from scratch Z to the band Mr.

After the Myosine and the Actine, the titine is the most abundant Protéine in the striated Muscle, accounting for some 10% of the mass myofibrillaire.

Structure

With approximately 30.000 amino-acid and a molecular Mass of 3.000 kDa, the titine is more the polypeptide large chain known. A Molécule extends from scratch Z to the line M, which represents close to a half Sarcomère, that is to say more than one microphone Mètre length.

On the level of the band has, the titine is mainly made up of repetitive structures of fields similar to the Immunoglobuline and the Fibronectine 3. It has multiple sites of fixing with the Myosine, the Protéine C or AMP désaminase.

On the level of band I, the titine is related to the calpaïne 3, proteolytic Enzyme Calcium - dependant endogenous person in charge of degradation on the contractile structure of the Muscle.

On the level of scratch Z, the association of the titine with the Actine guarantees the maintenance of the assembly myofibrillaire during muscular work.

Physiological functions

With the Nébuline, the titine is the principal one constituting longitudinal filaments which ensure the maintenance of architecture myofibrillaire. Thanks to its fixing and the interactions with several muscular Protein S - the such Actine, a-actinine, the Protein C, the Myosine, the myomésine or the m Protein -, the titine control the integrity and ensures the mechanical stability of the Sarcomère.

During muscular work, the deployment of the titine generates a force able to be opposed to the tension of stretching Sarcomère: during the contraction of a Muscle striated, the active tension comes from the action of the thin filaments of Actine on the thick filaments of Myosine and the passive tension results from the extension of the titine.

The titine would have a big role in the myofibrillogenèse.

The titine would be expressed in the Chromosome S, allowing their condensation at the time of the Mitose.

Pathologies

The titine is essential to the viability of the Sarcomère and its degradation weakens the Muscle. changes of the Gène of the titine - located on chromosome 2 (2q31-33) - are responsible for Myopathie S and muscular, severe Dystrophie S in the case of the Homozygote S.

At the people suffering from obtructive Broncho-pneumonopathy chronic, the expression of the titine is modified, so that the contractility of muscle fibers of the Diaphragme is faded.

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