Proteins that are excreted by prokaryotes are synthesized on ribosomes that are bound to the cytoplasmic surface of the plasma membrane.
In prokaryotes, the ribosomes that are used for the synthesis of secreted proteins are located outside of the cell.
Prokaryotes are unlikely to be able to excrete proteins because they lack an endomembrane system.
Prokaryotes contain large pores in their plasma membrane that permit the movement of proteins out of the cell.
The mechanism of protein excretion in prokaryotes is probably the same as that in eukaryotes.