Urea extraction of Z bands, intercalated disks, and desmosomes

Specific extraction of Z bands, intercalated disks and desmosomes was accomplished with molar concentrations of urea. Thick and thin filaments and M line material were undisturbed, demonstrating that the Z band protein is not similar to actin, myosin, or the M-line protein. The literature indicates that the tropomyosins are the only other structural proteins present in sufficient amounts to account for the extracted Z bands. However, the evidence for a lipid-protein association in the Z bands is considered and is further supported by the close association of the dense material of the Z bands, intercalated disks, and desmosomes with the lipoprotein cell membranes.