High-affinity binding of lower-density lipoproteins to chicken oocyte membranes.
Oocyte membrane fragments bind specifically radioiodinated VLD lipoprotein (very-low density lipoprotein) and LD lipoprotein (low-density lipoprotein). Competitive binding assays showed 2-3 times more VLD lipoprotein than LD lipoprotein bound at 4 degrees C. Equilibrium-binding data revealed the presence of one class of non-interacting sites for VLD lipoprotein (kD 12 microgram/ml) and co-operative binding for LD lipoprotein. The binding of VLD lipoprotein showed a distinct pH maximum at 5.3, whereas an indistinct maximum at about pH 7.3 was observed for LD lipoprotein. Unlabelled VLD lipoprotein did compete with 125I-labelled LD lipoprotein binding, but unlabelled LD lipoprotein did not compete with 125I-labelled VLD lipoprotein binding. VLD lipoprotein binding was inhibited by HD lipoprotein (high-density lipoprotein), but not by lysozyme, collagen, poly-L-lysine or poly-L-arginine; LD lipoprotein binding was inhibited by lysozyme and collagen, but not by HD lipoprotein. On the basis of these studies, we suggest that: (1) VLD lipoprotein and LD lipoprotein enter the oocytes by a receptor-mediated transport mechanism; (2) the receptors for VLD lipoprotein and LD lipoprotein are distinct; and (3) the binding of LD lipoprotein to chicken oocyte membranes differs from that to other cell types.
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008079:Lipoproteins, VLDL / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism*; D010063:Ovum / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D013696:Temperature
D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL