Degradation of Proteins Artificially Introduced into Vacuoles of Chara australis.

When an exogenous protein, bovine serum albumin, was introduced into the vacuole of a Chara australis internodal cell, it was degraded with time. This degradation proceeded only in the vacuole as far as could be observed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Degradation was inhibited by protease inhibitors such as antipain and leupeptin. Endogenous proteins introduced into the vacuole were also degraded there. Furthermore, intravacuolar cytoplasmic drops, which were often formed by cell ligation, seemed to be degraded in the vacuole. However, bovine serum albumin degradation did not proceed when mixed with isolated vacuolar sap. These results show that the vacuole in the Chara internodal cell has the capacity to degrade cellular proteins, but that cytoplasmic support is needed for this degrading activity to be maintained.