title: Conjugation of poly-L-lysine to albumin and horseradish peroxidase: a novel method of enhancing the cellular uptake of proteins.
abstract: The carbodiimide-catalyzed conjugation of a 6700 molecular weight fragment of poly-L-lysine to radiolabeled human serum albumin or to horseradish peroxidase enhances the membrane transport of each protein into cultured mouse fibroblasts approximately 11- and 200-fold, respectively. At least 50% of the peroxidase activity remained after conjugation. Trypsinization and carbamylation of the two conjugates demonstrates that the enhancement of their cellular uptake is related to their poly-L-lysine content. Simple addition to the medium of comparable amounts of free poly-L-lysine has no effect on the transport of either native protein. Addition of poly-L-ornithine (molecular weight 200,000) at 3-30 microgram/ml, a condition known to cause enhancement of 125I-labeled human serum albumin uptake by mouse sarcoma cells, has no visible effect on the cellular uptake of native horseradish peroxidase. The intracellular localization of the enzyme-poly-L-lysine conjugate can be demonstrated cytochemically by either light or transmission electron microscopy. A concentration of conjugate that increases the uptake more than 200-fold does not cause any detectable morphological change suggestive of cell toxicity. Furthermore, because poly-L-lysine is an excellent substrate for intracellular proteolytic enzymes, it can be expected to be broken down and reutilized in the cell.
mesh_terms: D001692:Biological Transport; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007739:L Cells; D009952:Ornithine / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D011107:Polylysine / Q000378:metabolism*; D012709:Serum Albumin / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D010455:Peptides; D012709:Serum Albumin; D011107:Polylysine; D009952:Ornithine; D006735:Horseradish Peroxidase; D010544:Peroxidases
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