The Structure of the Z-Band

During muscular contraction, the Z-band serves as an anchor for the myosin filaments. These filaments are antiparallel and crosslink opposite polarities. In addition, the Z-band transmits tension along the myofibrils.

Z-bands are found in skeletal muscle of many vertebrates. Their width and structure vary depending on the type of muscle. For example, in slow skeletal muscles, the Z-band is wider than in cardiac muscle. In fast skeletal muscles, however, the Z-band is narrower than in slow muscle.

In striated muscle, the Z-band borders the sarcomeres. It also connects thin filament arrays in the contractile apparatus. Several studies have investigated the structural details of the Z-band. Some of these studies used electron microscopy. Others used Fourier analysis.

Electron microscopy studies of transverse sections of striated muscle in vertebrates show two distinct structures. The first is a small square lattice. The other is a basketweave lattice. These structures are similar in appearance to the nemaline rods, which are often found in patients with nemaline myopathy.

In the first study, Morris etal. used Fourier methods to generate a three-dimensional (3D) picture of the Z-band. They showed the path of a-actinin, a-actinin layers, and actin binding domains. They used this method to generate 3D images of Z-bands in nemaline rods and in two different types of muscle.

In the second study, Luther etal. studied the Z-band in a rat cardiac muscle. They used Morris's method to generate 3D images of the Z-band in two muscles. They also used tilt series techniques to analyse the white muscles of fishes.