Abstract: The present invention relates to multifunctional protein production tags comprising at least 4, preferably 4-8 amino acids, for optimising expression of proteins and purification thereof by various multi-step processes including chromatographic or filtration, as well as batch unit operations. The tags include sequences of multiple defined purposes which are not generated in defined linear sequence regions related to one purpose but as integrated sequences often overlapping each other, i.e. the defined purposes are not discrete separate units on the tag but rather heterogeneously distributed in the tag. The invention also relates to an expression vector encoding the multipurpose tag and a method for protein purification, comprising expressing a protein in the expression vector and purifying the protein in several steps using functionalities of the multipurpose tag.