6-535: The WD40 repeat (also known as the WD or beta-transducin repeat ) is a short structural motif of approximately 40 amino acids , often terminating in a tryptophan - aspartic acid (W-D) dipeptide. Tandem copies of these repeats typically fold together to form a type of circular solenoid protein domain called the WD40 domain . WD40 domain-containing proteins have 4 to 16 repeating units, all of which are thought to form
12-421: A sequence motif ; it can be represented by different and completely unrelated sequences in different proteins or RNA. Depending upon the sequence and other conditions, nucleic acids can form a variety of structural motifs which is thought to have biological significance. In proteins, a structural motif describes the connectivity between secondary structural elements. An individual motif usually consists of only
18-436: A circularised beta-propeller structure (see figure to the right). The WD40 domain is composed of several repeats, a variable region of around 20 residues at the beginning followed by a more common repeated set of residues. These repeats typically form a four stranded anti-parallel beta sheet or blade. These blades come together to form a propeller with the most common being a 7 bladed beta propeller. The blades interlock so that
24-400: Is coordinating multi-protein complex assemblies, where the repeating units serve as a rigid scaffold for protein interactions. The specificity of the proteins is determined by the sequences outside the repeats themselves. Examples of such complexes are G proteins (beta subunit is a beta-propeller), TAFII transcription factor, and E3 ubiquitin ligase . According to the initial analysis of
30-493: The human genome WD40 repeats are the eighth largest family of proteins. In all 277 proteins were identified to contain them. Human genes encoding proteins containing this domain include: Structural motif In a chain-like biological molecule , such as a protein or nucleic acid , a structural motif is a common three-dimensional structure that appears in a variety of different, evolutionarily unrelated molecules. A structural motif does not have to be associated with
36-404: The last beta strand of one repeat forms with the first three of the next repeat to form the 3D blade structure. WD40-repeat proteins are a large family found in all eukaryotes and are implicated in a variety of functions ranging from signal transduction and transcription regulation to cell cycle control, autophagy and apoptosis . The underlying common function of all WD40-repeat proteins
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