Troponina T tipo 3

A troponina T, músculo esquelético rápida ou troponina T tipo 3 (TNNT3) é unha proteína situada nos miofilamentos finos das fibras musculares estriadas esqueléticas, que nos humanos está codificada no xene TNNT3 do cromosoma 11.^[1][2] É unha das tres isoformas da troponina T; as outras dúas son TNNT1 e TNNT2. Esta isoforma exprésase no músculo esquelético de contracción rápida. A troponina T únese á tropomiosina situándoa sobre os filamentos de actina do sarcómero muscular tapando os sitios da actina para a unión coa miosina, o que impide a contracción muscular. A troponina é un complexo proteico que regula a contracción muscular formado por tres subunidades, que son as troponinas T, C e I.

O xene TNNT3 ten unha lonxitude de 19 kb e contén 19 exóns, entre eles hai 2 que son específicos da TNNT3 fetal ou neonatal (isoforma beta), que non se expresan no adulto (que expresa a isoforma alfa, que se diferencia en 14 aminoácidos do extremo C-terminal). O splicing alternativo deste xene pode orixinar varios transcritos distintos para esta proteína. As mutacións neste xene poden orixinar artrogripose distal múltiple conxénita tipo 2B (AD2B).^[3]

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