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J Biol Chem. 2012 May 25;287(22):18153-62. doi: 10.1074/jbc.M111.284521. Epub 2012 Mar 27.

Novel mutation in spectrin-like repeat 1 of dystrophin central domain causes protein misfolding and mild Becker muscular dystrophy.

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1
Connecticut Children's Medical Center, Hartford, Connecticut 06106, USA.

Abstract

Mutations in the dystrophin gene without disruption of the reading frame often lead to Becker muscular dystrophy, but a genotype/phenotype correlation is difficult to establish. Amino acid substitutions may disrupt binding capacities of dystrophin and have a major impact on the functionality of this protein. We have identified two brothers (ages 8 and 10 years) with very mild proximal weakness, recurrent abdominal pain, and moderately elevated serum creatine kinase levels. Gene sequencing revealed a novel mutation in exon 11 of the dystrophin gene (c.1280T>C) leading to a L427P amino acid substitution in repeat 1 of the central rod domain. Immunostaining of skeletal muscle showed weak staining of the dystrophin region encoded by exons 7 and 8 corresponding to the end of the actin-binding domain 1 and the N-terminal part of hinge 1. Spectrofluorescence and circular dichroism analysis of the domain repeat 1-2 (R1-2) revealed partial misfolding of the L427P mutated protein as well as a reduced refolding rate after denaturation. Based on computational homology models of the wild-type and mutated R1-2, a molecular dynamics study showed an alteration in the flexibility of the structure, which also strongly affects the conformational space available in the N-terminal region of the fragment. Our results suggest that this missense mutation hinders the dynamic properties of the entire N-terminal region of dystrophin.

PMID:
22453924
PMCID:
PMC3365720
DOI:
10.1074/jbc.M111.284521
[Indexed for MEDLINE]
Free PMC Article
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