Walker's A and B-box consensus sequences
Those sequences are nucleotide binding sites, e.g. in
Apaf-1.
WD-40 repeats
Loosely conserved set of sequences which is found in many regulatory proteins, including beta-subunits of
heterotrimeric G proteins, the SREBP cleavage-activating protein, but also in Apaf-1.
In Apaf-1, the WD-40 repeats have an inhibitory effect on caspase-9 activation by Apaf-1, which is relieved after cyto c
binding in the presence of dATP, allowing the formation of a multimeric Apaf-1/cyto c complex.
WW domain
The WW domain is a short motif that can bind phosphoserine or phosphothreonine residues. Its name derives from the presence of
two conserved tryptophane residues. WW domains were identified in several members of the E3 ubiquitin ligase family,
presumably contributing to substrate-specific binding and ubiquitination.