The present invention relates to an allergen from banana, designed as Mus a 5, which is produced b\ recombinant DNA technology in E. coli cells. Mus a 5 polypeptide, a vector and a host cell for the production, the method of production, and a method for purifying a Mus 5 in the native conditions, for use in diagnostic purposes are provided. The composition and methods for the testing of diseases such as allergy to bananas are also provided. The yield of the preparation was above 15 mg from 1L of cell culture. The present invention may be utilized for in vitro and in vivo diagnosis of allergies in a banana.Predmetni pronalazak ce odnosi na alergen iz banane, označen sa Mus a 5, koji je proizveden tehnologijom rekombinantne DNK u ćelijama E. coli. Opisan je Mus a 5 polipeptid, vektor i ćelije domaćina za proizvodnju, postupak proizvodnje, i postupak prečišćavanja Mus a 5 u nativnim uslovima. za korišćenje u dijagnostičke svrhe. Preparat i postupci za testiranje oboljenja kao što su alergija na bananu su. takođe, obezbeđeni. Prinos preparata je preko 15 mg iz 1L ćelijske kulture. Predmetni pronalazak može da bude korišćen za in vilro i in vivo dijagnostiku alergije na bananu.