Structural studies of the Ig58 domain of the giant muscle protein obscurin

Obscurin (720-900 kD) is a giant sarcomeric signaling protein that is the only known link between the cytoskeleton and the surrounding membrane structure. Mutations to obscurin and to obscurin binding partners have been linked to human muscle diseases such as hypertrophic cardiomyopathies and muscular dystrophy. These diseases likely occur due to the abrogation of specific molecular interactions necessary for suitable function. To more fully understand how specific mutations lead to disease, here we solve the highresolution structure of obscurin Ig58. The literature shows that an Arg8Gln mutation to the Ig58 domain of obscurin is associated with hypertrophic cardiomyopathy (HCM). Chemical shift changes of this mutation and MD simulations suggest that this mutation disrupts a large charge-charge surface of Ig58, perturbing the titin-binding interface