Ribbon diagram of the C-terminal WD40 domain of Tup1 (a transcriptional co-repressor in yeast), which adopts a 7-bladed beta-propeller fold. Ribbon is colored from blue (N-terminus) to red (C-terminus). PDB1erj
In structural biology, a beta-propeller is a type of all-β protein architecture characterized by 4 to 8 blade-shaped beta sheets arranged toroidally around a central axis. Each sheet typically has four antiparallel β-strands twisted so that the first and fourth strands are almost perpendicular to each other. The enzyme's active site is often found in the cleft formed in the center of the propeller by loops connecting the successive four-sheet motifs. Murzin proposed a geometric model to describe the structural principles of the beta propeller. According to this model the seven bladed propeller was the most favoured arrangement in geometric terms.
A beta-propeller is a critical component of LDLR (low density lipoprotein receptor) and aids in a pH based conformational change. At neutral pH the LDLR is in an extended linear conformation and can bind ligands (PCSK9). At acidic pH the linear conformation changes to a hairpin structure such that ligand binding sites bind to the beta-propeller, preventing ligand binding.
^Murzin AG (October 1992). "Structural principles for the propeller assembly of beta-sheets: the preference for seven-fold symmetry". Proteins. 14 (2): 191–201. doi:10.1002/prot.340140206. PMID1409568.
^Neer EJ, Schmidt CJ, Nambudripad R, Smith TF (September 1994). "The ancient regulatory-protein family of WD-repeat proteins". Nature. 371 (6495): 297–300. doi:10.1038/371297a0. PMID8090199.