Contribution of the carboxy-terminal domain of lipoprotein lipase to interaction with heparin and lipoproteins

The C-terminal domain of Lipoprotein lipase (LPL) is involved in several im portant interactions. To assess its contribution to the binding ability of full-length LPL we have determined kinetic constants using biosensor techni que. The affinity of the C-terminal domain for heparin was about 500-fold l ower than that of full-length LPL (K-d = 1.3 mu M compared to 3.1 nM). Repl acement of Lys403, Arg405 and Lys407 by Ala abolished the heparin affinity, whereas replacement of Arg420 and Lys422 had little effect. The C-terminal domain increased binding of chylomicrons and VLDL to immobilized heparin r elatively well, but was less than 10% efficient in binding of LDL compared to full-length LPL, Deletion of residues 390-393 (WSDW) did not change the affinity to heparin and only slightly decreased the affinity to lipoprotein s. We conclude that the C-terminal folding domain contributes only moderate ly to the heparin affinity of full-length LPL, whereas the domain appears i mportant for tethering triglyceride-rich lipoproteins to heparin-bound LPL. (C) 2000 Academic Press.