Comparison of heterologous signals from human origin. The secretion signals of human blood clotting factor IX (FSP) as well as human vascular endothelial growth factor (VSP) were fused to the coding sequence of vascular endothelial growth factor (hVEGF). Moss protoplasts were transiently transfected with the expression constructs and concentration of extracellular as well as intracellular rhVEGF was determined by ELISA. Mean values were taken from three transfections. Error bars indicate the absolute average deviation (AAD).