ABSTRACT
A cell is a multiphase system composed of a lipid-containing membrane phase, a cyto-skeletal phase of polymerized proteins, and a cytosol phase containing proteins soluble at an ionic strength of 0.15. Cross-linking studies on extracellular proteins such as fibrin have led to habits of thought which see Glu-Lys cross-linking as a one-way phenomenon. To test whether Glu-Lys cross-link modulation occurs rapidly in whole cells we measured cross-link content before and after rapidly lowering their temperature from 37 to 4°C. K. E. Wohlfarth-Bottermann and co-workers have demonstrated that a coherent covalently cross-linked cytomatrix of super thin filaments, indeed, exists in the slime mold Physarum polycephalum. The portion of the super thin filaments running through the thick filaments may well consist of covalently cross-linked myosin rods or protein chains homologous to those of myosin rods. Transmission electron micrographs of our muscle fiber ghosts show what we interpret to be the greatly enlarged Z discs with super fine filaments extending between them.
