A pro-polypeptide which is useful for the expression of a polypeptide of interest in a prokaryotic cell. Therefore the pro-polypeptide is fused to the N-terminus of the polypeptide of interest. The pro-polypeptide as reported herein provides for improved expression yields and improves the handling of the fusion polypeptide (downstream processing, purification). For example, efficient endotoxin removal is effected while the protein of interest comprising the pro-polypeptide is bound e.g. to an affinity chromatography material. Thereafter the pro-polypeptide can efficiently be cleaved from the polypeptide of interest by the incorporated protease cleavage site with the cognate protease.