Autodegradation of 125I-labeled human epidermal cell surface proteins.
Triton X-100 extracts of cultured human epidermal cells exhibited proteolytic activity as measured by the hydrolysis of [3H]-casein at neutral pH. The majority of endogenous proteolytic activity was inhibited by parahydroxy mercuribenzoate and by mersalyl acid, indicating the enzyme(s) was a thiol class proteinase(s). Crude Triton X-100 extracts were prepared from epidermal cells following labeling of proteins with 125I. Autodegradation of labeled proteins at 37 degrees C was detected as early as 1 hr and reached a plateau level by 4 hr. Degradation was inhibited by thiol class proteinase inhibitors. Among the detergent-solubilized radiolabeled proteins a polypeptide chain of Mr 155,000 was particularly sensitive to degradation by endogenous thiol proteinase(s).
D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000378:metabolism*; D004817:Epidermis / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods; D007784:Lactoperoxidase / Q000378:metabolism; D008297:Male; D017830:Octoxynol; D011092:Polyethylene Glycols; D011506:Proteins / Q000378:metabolism*; D013997:Time Factors
D007457:Iodine Radioisotopes; D011506:Proteins; D011092:Polyethylene Glycols; D017830:Octoxynol; D007784:Lactoperoxidase; D010450:Endopeptidases