Concentrations of secreted recombinant GST. Physcomitrella protoplasts were transiently transfected with pVSP-GST and pASP-GST in eight independent transfections. After 5 days the concentrations of secreted and intracellularly-retained recombinant protein were measured by ELISA. Additionally, GST was affinity-purified from both medium and supernatant and detected by western blot. A: Culture medium of two transfections was pooled. Mean values of eight transfections are given. B: Protoplasts of eight transfections were pooled and GST was affinity-purified from the crude extracts. Values reflect the means of the two measurements. Control: mock-transfected protoplasts.