Structure and Mutation Analysis of the C2A Domain of Human Dysferlin Provides a Thermodynamic Basis for Limb-Girdle Muscular Dystrophy

Limb-Girdle muscular dystrophy (LGMD) is the collective term describing a neuromuscular condition that results from mutation in one of ∼16 muscle-related genes. Patients with slowly progressing LGMD may be able to walk for about 30 years after disease onset, but many will become wheelchair bound in their teens. LGMD-2B is a sub-type in this class of muscular dystrophy and involves mutations within the dysferlin gene. This form of LGMD is responsible for up to 20% of all clinically described cases in the US. In many cases, point mutations within one of the seven C2 domains of dysferlin are sufficient to cause disease. We have crystallized and solved the X-ray crystal structure of the C2A domain of human dysferlin to 2.0A resolution. Biophysical analysis of the wt and V67D mutation of the C2A domain of dysferlin shows that while the domain is folded, it is thermodynamically unstable. This compromised stability is likely due to the un-satisfied charge buried in the core of the domain.