WD repeats are defined by the presence of four or more repeating units containing a conserved core of about 40 amino acids, usually terminating with tryptophan aspartic acid (WD). Within this protein family, WD repeat domains are thought to share two common features:
WD repeat proteins occupy a key role in the formation of protein-protein complexes in almost all major metabolic pathways and organelles unique to eukaryotic cells. The importance of these proteins is not only reflected in their important role in many essential biological functions ranging from signal transduction to transcriptional regulation and apoptosis (Smith TF 2008). It is of great importance for the understanding of diseases to uncover the function of individual WD repeat proteins, to explore the protein interaction mechanism through WD repeat domains, and ultimately to understand the complex biological processes and organisms themselves (Li D et al. 2001).