Different obscurin isoforms localize to distinct sites at sarcomeres

Abstract

We used four antibodies to regions of obscurin isoforms A and B, encoded by the obscurin gene, to investigate the location of these proteins in skeletal myofibers at resting and stretched lengths. Obscurin A (∼800 kDa) which was recognized by antibodies generated to the N‐terminal, Rho‐GEF, and the non‐modular C‐terminal domain that lacks the kinase‐like domains, localizes at the level of the M‐band. Obscurin B (∼900 kDa) which has the N‐terminal, Rho‐GEF, and the C‐terminal kinase‐like domains, localizes at the level of the A/I junction. Additional isoforms, which lack one or more of these epitopes, are present at the Z‐disk and Z/I junction.