The effect of negatively charged liposome on in vitro synthesis of a reporter protein, green fluorescent protein (GFP), was investigated using a cell-free translation system. GFP was expressed with and without negatively charged liposome prepared with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylchorine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG), resulting in the GFP fluorescence being reduced to approximately 60% in the presence of POPC/POPG at more than 30% POPG, depending on its concentration. However, the amount of synthesized GFP products, as analyzed by SDS-PAGE, did not change with and without the POPC/POPG liposome. The results of the ultrafiltration operation indicate that the liposome interacts not only with synthesized polypeptide GFP but also with folded synthesized GFP (mature GFP). Liposome also inhibited refolding of unfolded GFP to its native state. The above results show that the POPC/POPG could inhibit the folding of GFP in the post-translational process of the gene expression product.
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