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„Yeast surface display“ sustav predstavlja metodu imobilizacije rekombinantnih proteina na površinu stanice kvasca pri čemu se gen koji kodira za željeni protein fuzionira sa čitavim genom ili fragmentom gena koji kodira za jedan od proteina stanične stijenke. Ova genetička fuzija omogućuje ekspresiju i ugradnju rekombinantnog proteina u staničnu stijenku kvasca. Osnovni nedostatci ove metode su relativno mala količina na površinu stanice ugrađenih rekombinantnih proteina, potencijalno smanjenje aktivnost rekombinantnih proteina uslijed fuzije sa proteinom stijenke te ponekad njihova hiperglikozilacija. Glikozilacija je postsintetska preinaka proteina koja može utjecati na smatanje, aktivnost i stabilnost proteina. Cilj ovog rada jest ispitati utjecaj O-glikozilacije na efikasnost ugradnje i aktivnost rekombinantnog enzima β-laktamaze u staničnu stijenku. Gen koji kodira za ovaj enzim je u jednom slučaju fuzioniran sa genom koji kodira za Pir2, a u drugom slučaju sa dijelom gena koji kodira za Ccw12 protein stijenke. Rekombinantni enzim eksprimiran je u stanicama kvasca divljeg tipa i u stanicama koji imaju mutaciju u O-glikozilaciji proteina (pmt mutanti). Količina enzima koja se ugradila u stijenku analizirana je mjerenjem aktivnosti enzima korištenjem nitrocefina kao supstrata i western blot analizom. Yeast „surface display“ system represents an alternative method of immobilization of recombinant proteins on the yeast cell wall surface in which the gene encoding for the protein of interest is fused with whole or with fragment of a gene encoding for a native yeast cell wall proteins. This genetic fusion provides constant expression and incorporation of the recombinant protein into the cell wall. However, one of the major disadvantages of this method are relatively low yield of the recombinant protein in the cell wall, potential low activity of incorporated recombinant protein due to their fusion with native cell wall protein and their hypermannosylation. Glycosylation is one of major posttranslational modifications which effects protein folding, their activity and stability. Theme of this thesis is to study the effect of O-glycosylation on incorporation of the recombinant enzyme β-lactamase into the cell wall. In one case, the gene encoding for this enzyme is fused with gene encoding for Pir2 protein, and in the other the gene is fused with the gene encoding for Ccw12 protein. The recombinant enzyme was expressed in the wild type yeast cells and in O-glycosylation mutants (pmt mutants). The amount of enzyme in the cell wall is assessed by measuring β-lactamase activity using nitrocefine as substrate and by western blot. |
