Title
High affinity binding of the receptor-associated protein D1D2 domains with the LDL receptor-related protein (LRP1) involves bivalent complex formation: Critical roles of lysine 60 and 191.
Author
Joni M. Prasad, Patricia A. Young, Dudley K. Strickland
Year
2016
Journal
The Journal of Biological Chemistry
Abstract
The LDL receptor-related protein 1 (LRP1) is a large endocytic receptor that binds and mediates the endocytosis of numerous structurally diverse ligands. Currently, the basis for ligand recognition by LRP1 is not well understood. LRP1 requires a molecular chaperone, termed the receptor-associated protein (RAP), to escort the newly synthesized receptor from the endoplasmic reticulum to the Golgi. RAP is a three domain protein that contains two high affinity binding sites for LRP1: one located within domains 1 and 2, and one located in its third domain. Studies on the interaction of the RAP third domain with LRP1 reveal critical contributions by lysine 256 and lysine 270 for this interaction. From these studies, a model for ligand recognition by this class of receptors has been proposed. Here we employed surface plasmon resonance to investigate the binding of RAP D1D2 to LRP1. Our results reveal that the high affinity of D1D2 for LRP1 results from avidity effects mediated by the simultaneous interactions of lysine 60 in D1 and lysine 191 in D2 with sites on LRP1 to form a bivalent D1D2/LRP1 complex. When lysine 60 and 191 are both mutated to alanine, the binding of D1D2 to LRP1 is ablated. Our data also reveal that D1D2 is able to bind to a second distinct site on LRP1 to form a monovalent complex. The studies confirm the canonical model for ligand recognition by this class of receptors which is initiated by pairs of lysine residues that dock into acidic pockets on the receptor.
Instrument
J-715
Keywords
Circular dichroism, Secondary structure, Protein denaturation, Protein folding, Thermal stability, Biochemistry