Synthetic fragments of apo-C-II, specifically labeled on their NH2-terminals with the 5-dimethylaminonaphthalene-1-sulfonyl (dansyl or DNS) fluorophore, have been prepared by solid phase peptide synthesis. When a complex is formed between bovine milk lipoprotein lipase and N-dansyl-apo-C-II peptides, resonance energy transfer occurs from the tryptophan residues of the enzyme to the dansyl-labeled peptides upon excitation at 280 nm. In the absence of lipid, the association constant increases 10-fold when the length of the DNS peptide is increased from apo-C-II-DNS(64-78) (0.04 x 106 M-1) to apo-C-II-DNS(60-78) (0.3 x 106 M-1). In the presence of lipid, the association constants are dependent on peptide chain length, and increase from 0.4 x 106 M-1 for apo-C-II-DNS(64-78) to 2.2 x 107 M-1 for apo-C-II-DNS(43-78). The interactions are specific for lipoprotein lipase, are disrupted by guanidinium chloride, are not affected by 1.0 M NaCl, and are competitive with the corresponding nondansylated peptide. Apolipoproteins C-III and A-I, at 5 to 1 molar ratios, had no effect on the interaction. These findings demonstrate the importance of the COOH-terminal region in the lipoprotein lipase-apo-C-II interaction and show that activation of the enzyme involves a specific protein-protein interaction.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|State||Published - 1983|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology