Growth and the cell cycle of the yeast Saccharomyces cerevisiae. I. Slowing S phase or nuclear division decreases the G1 cell cycle period

To determine changes in distribution or mobility of cell-surface glycoconjugates during myogenesis the binding of fluorescein-conjugated plant lectins to myoblasts and myotubes of the L6 rat skeletal muscle cell line has been studied. Binding has been carried out at 4 degrees C on either live or glutaraldehyde-fixed cells. Fluorescein conjugates of soybean agglutinin (Fl-SBA), wheat germ agglutinin (Fl-WGA), concanavalin A (Fl-conA) and Lens culinaris agglutinin (Fl-LCA) produced predominantly uniform fluorescence on both live and fixed myoblasts. On fixed myotubes, Fl-LCA, Fl-conA and Fl-SBA again produced predominantly uniform fluorescence, whereas Fl-WGA showed a pattern of diffuse, irregular spots in addition to uniform fluorescence. Fl-conA, Fl-LCA and Fl-WGA binding to live myotubes resulted in patterns quite similar to those on fixed myotubes; the only differences being the presence of weak patterns of diffuse spots with Fl-LCA and Fl-conA and an enhanced pattern of diffuse spots with Fl-WGA. Fl-SBA, however, showed a unique pattern on live myotubes which consisted of discrete, round spots and minimal uniform fluorescence. With shorter labeling times, Fl-SBA produced relatively more prominent uniform fluorescence on live myotubes. It appears, therefore, that the native distribution of SBA, conA and LCA-binding sites is similar and predominantly random on L6 myoblasts and myotubes, whereas some WGA-binding sites may be aggregated on myotubes. The results also suggest that SBA-binding sites readily cluster at 4 degrees C on myotubes but not myoblasts, whereas the other lectin sites undergo little or no redistribution on either cell type. Thus the mobility of SBA-binding sites may increase with differentiation.