Disclosed is a polypeptide comprising at least two microproteins, which preferably comprise an amino acid sequence having a specific binding activity to a target protein. Furthermore, disclosed are polynucleotides encoding such a polypeptide as well as pharmaceutical compositions and kits comprising said polypeptide or polynucleotide. Also disclosed herein are methods of treatments and second medical uses applying the disclosed polypeptide or polynucleotide. Additionally, the disclosure of the present application relates to a method for forming a covalent bond in a microprotein which can be used for producing the disclosed polypeptides.