Isozymes of ribonuclease and the changes in their relative levels during development in the cellular slime mould Dictyostelium discoideum

The isozymes of ribonuclease were analyzed in cell-free, crude extracts of Dictyostelium discoideum by activity staining of polyacrylamide gels after electrophoresis. The relative levels of three isozymes were then examined during the growth and during the first stages of multicellular development. We observed the replacement of two of these three isozymes by two other isozymes at the pseudoplasmodial stage. These isozymes were different from ribonuclease T1 in terms of their mobility in polyacrylamide gels during electrophoresis. The mobilities of two of the isozymes, DdI and DdII, were 59 and 42% of that of ribonuclease T1. The changes in the relative levels of the isozymes during development are discussed.