Z-Nin, a New High Molecular Weight Protein Required for Reconstitution of the Z-Disk

Abstract

The materials released from myofibrils by Ca²⁺ -activated factor (CAF) were fractionated by
using a combination of Sepharose 6B and Bio-gel A 50m columns. To investigate the exact constituents of Z-disks on the basis of success or failure of reconstitution of Z-disks, reconstitution of Z-disks by incubating individual fractions with Z-disk-extracted fiber bundles was carried out, and the proteins in each fraction were analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis.
From the electron micrographs of the reconstituted Z-disks, SDS-polyacrylamide gel electrophoretic analysis and amino acid analysis of the isolated proteins from the gels, it was clear that the proteins required for the reconstitution of the Z-disk, in other words, the principal constituents of the Z-disk, were Z-nin, a new high molecular weight protein having a subunit molecular weight of 300, 000-400, 000 dalton mentioned in this report, α-actinin and tropomyosin.