Dystrophin

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dystrophin (muscular dystrophy, Duchenne and Becker types)
Identifiers
Symbol(s)	DMD
Entrez	1756
OMIM	300377
RefSeq	NM_004006
UniProt	P11532
Other data
Locus	Chr. X p21.2

Dystrophin is a rod-shaped protein, and a vital part of a protein complex which connects the cytoskeleton of a muscle fiber to the surrounding extracellular matrix through the cell membrane.

Dystrophin has the longest gene known to date, measuring 2.4 megabases. Its gene's locus is Xp21 and has 79 exons spanning 2.5 megabases, produces an mRNA of 14.6 kilobases and a protein of over 3500 amino acid residues. The gene is so large it accounts for 0.1% of the human genome.

[edit] Pathology

Its deficiency is one of the root causes of muscular dystrophy. It was first identified in 1987 by Louis M. Kunkel, after the 1986 discovery of the mutated gene that causes Duchenne muscular dystrophy (DMD).

Normal tissue contains small amounts of dystrophin (about 0.002% of total muscle protein), but its absence leads to both DMD and fibrosis, a condition of muscle hardening. A different mutation of the same gene causes defective dystrophin, leading to Becker's muscular dystrophy (BMD).