Puromycin is an aminonucleoside antibiotic, derived from the Streptomyces alboniger bacterium, that causes premature chain termination during translation taking place in the ribosome. Pa of the molecule resembles the 3&; end of the aminoacylated tRNA. It enters the A site and transfers to the growing chain, causing the formation of a puromycylated nascent chain and premature chain release. The exact mechanism of action is unknown at this time but the 3&; position contains an amide linkage instead of the normal ester linkage of tRNA. That makes the molecule much more resistant to hydrolysis and stops the ribosome.Puromycin is selective for either prokaryotes or eukaryotes.Also of note, puromycin is critical in mRNA display. In this reaction, a puromycin molecule is chemically attached to the end of an mRNA template, which is then translated into protein. The puromycin can then form a covalent link to the growing peptide chain allowing the mRNA to be physically linked to its translational product.Antibodies that recognize puromycylated nascent chains can also be used to purify newly synthesized polypeptides and to visualize the distribution of actively translating ribosomes by immunofluorescence.Ref: https://en.wikipedia.org/wiki/Puromycin