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Domain 2 of receptor-associated protein (RAP) This subfamily is the N-terminal domain (D2) of receptor-associated protein, RAP, an antagonist and a specialized chaperone in the endoplasmic reticulum that binds tightly to members of the low-density lipoprotein (LDL) receptor family and prevents them from associating with other ligands. D2, along with RAP domain 1 (D1), is essential for blocking low-density lipoprotein receptor-related protein (LRP) from binding of certain ligands, such as alpha2-macroglobulin; D1 and D2 each bind LRP weakly but the tandem D1D2 binds much more tightly to the second and the fourth ligand-binding clusters present on LRP, suggesting the avidity effects arising from amino acid residues contributed from each domain. Also, RAP has regions that interact weakly with heparin, one located in D2 and two located in D3. The double module of complement type repeats, CR56, of LRP binds many ligands including alpha2-macroglobulin, which promotes the catabolism of the Abeta-peptide implicated in Alzheimer's disease. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",