Chemotactic properties, cellular binding and uptake of peptides and peptide derivatives: studies with Tetrahymena thermophila.
Receptor-mediated binding of leukocyte chemotactic peptide, N-formylMet-Leu-Phe (fMLP), occurs in the ciliated protozoon Tetrahymena thermophila. In vivo labelling of the cells with N-formylMet-Leu-[3H]Phe ([3H]fMLP) shows that the cells bind the ligand with high affinity (KD = 4 x 10(-9) M to 1 x 10(-8) M). Moreover, Scatchard transformations of the binding data show that there are about 5 x 10(5) binding sites per cell on the cell surface. Two fluorescent derivatives of leukocyte chemotactic peptide, N-dansylMet-Leu-Phe (dansMLP) and N-formylMet-Leu-Phe-(N-dansyl-)Lys (fMLPdanLys) compete for the N-formylMet-Leu-Phe (fMLP) binding sites on the cell surface. Moreover, both derivatives have retained significant chemoattracting potentials. Fluorescence from dansMLP, but not from fMLPdansLys and dansyl-beta-endorphin, is internalized preferentially into small vesicles. The differences may, however, reflect that the fluorescence from the dansyl group is strongly quenched by a hydrophilic microenvironment when using the two latter peptide derivatives. In contrast, the dansyl group from dansMLP must be assumed to be embedded in a hydrophobic microenvironment in the vesicular membrane or membrane protein. Rhodamine-labelled bovine serum albumin, egg albumin and cytochrome c as well as dansylated bovine serum albumin, which are poor chemoattractants, are preferentially seen to be internalized into large vesicles (food vacuoles).
Leick
V
V
Department of Biochemistry, University of Copenhagen, Denmark.
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001693:Biological Transport, Active; D002633:Chemotaxis / Q000187:drug effects; D003619:Dansyl Compounds / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology; D016808:Tetrahymena thermophila / Q000187:drug effects / Q000378:metabolism*
D003619:Dansyl Compounds; C079070:N-formylmethionyl-leucyl-phenylalanyl-(N-dansyl)lysine; D009842:Oligopeptides; C079071:N-dansylmethionyl-leucyl-phenylalanine; D009240:N-Formylmethionine Leucyl-Phenylalanine