The dynamic Z bands of striated muscle cells.

The distribution of proteins in the sarcomeres of skeletal and cardiac muscle gives rise to the striated pattern of these muscles. Sarcomeric protein localization is not, however, permanently fixed. There is dynamic exchange of proteins between a cytosolic pool and the sarcomere, addition of newly synthesized proteins during development and repair, and aberrant redistribution of proteins due to mutations. Recent studies have shown that two groups of proteins that localize in the sarcomere Z band can relocate, in one case to the A band, and in the other to the nucleus.