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first cysteine-rich (Cys-1) domain of Dickkopf-related protein 2 Dickkopf 2 (Dkk2) is a secreted protein which directly binds to LRP5/6 (low-density lipoprotein receptor related protein 5 and 6), and is an inhibitor of Wnt/beta-catenin signaling. Dkk2 expression is modulated by expression of micro RNA-221 (miRNA-221) in esophageal cancer, and inactivation of Dkk2 may increase Wnt activity with accelerating tumor progression. Dkk2 belongs to the Dickkopf (Dkk) family that comprises a discrete class of secreted Wnt inhibitors. The Wnt gene family is a large class of secreted proteins that are expressed in a variety of tissues and organs, and are required for many developmental processes, including segmentation, endoderm development, limb polarity, neural crest differentiation, kidney morphogenesis, sex determination and brain development. Dkks 1-4 each possesses an N-terminal signal peptide and contains two conserved cysteine-rich domains (Cys-1 and Cys-2) separated by a linker region. Each domain possesses 10 conserved cysteine residues. The Cys-2 domain is closely similar to those in the colipase family; it has been suggested that the Cys-2 domain of Dkks may enable interaction with lipids in order to regulate Wnt function. This model corresponds to the Cys-1 domain of Dkk2. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",