WD40 repeat

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. Several of these repeats are combined to form a type of protein domain called the WD domain.

Structure
WD-containing proteins have 4 to 16 repeating units, all of which are thought to form a circularised beta-propeller structure (see figure to the right).

Function
WD-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 and apoptosis. The underlying common function of all WD-repeat proteins 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.

Examples
Human genes encoding proteins containing this domain include:


 * AAAS, AAMP, AHI1, AMBRA1, APAF1, ARPC1A, ARPC1B, ATG16L1,
 * BOP1, BRWD1, BRWD2, BRWD3, BTRC, BUB3,
 * C6orf11, CDC20, CDC40, CDRT1, CHAF1B, CIAO1, CIRH1A, COPA, COPB2, CORO1A, CORO1B, CORO1C, CORO2A, CORO2B, CORO6, CORO7, CSTF1,
 * DDB2, DENND3, DMWD, DMXL1, DMXL2, DNAI1, DNAI2, DNCI1, DTL, DYNC1I1, DYNC1I2, EDC4,
 * EED, EIF3S2, ELP2, EML1, EML2, EML3, EML4, EML4-ALK, EML5, ERCC8,
 * FBXW10, FBXW11, FBXW2, FBXW4, FBXW5, FBXW7, FBXW8, FBXW9, FZR1,
 * GBL, GEMIN5, GNB1, GNB1L, GNB2, GNB2L1, GNB3, GNB4, GNB5, GRWD1, GTF3C2,
 * HERC1, HIRA, HZGJ,
 * IFT122, IFT140, IFT172, IFT80, IQWD1,
 * KATNB1, KIAA1336, KIF21A, KIF21B, KM-PA-2,
 * LLGL1, LLGL2, LRBA, LRWD1, LYST,
 * MAPKBP1, MED16, MORG1,
 * NBEA, NBEAL1, NEDD1, NLE1, NSMAF, NUP37, NUP43, NWD1,
 * PAAF1, PAFAH1B1, PAK1IP1, PEX7, PHIP, PIK3R4, PLAA, PLRG1, PPP2R2B, PPP2R2C, PPWD1, PREB, PRPF19, PRPF4, PWP1, PWP2,
 * RAE1, RAPTOR, RBBP4, RBBP5, RBBP7, RFWD2, RFWD3, RRP9,
 * SCAP, SEC13, SEC31A, SEC31B, SEH1L, SHKBP1, SMU1, SPAG16, SPG, STRAP, STRN, STRN3, STRN4, STXBP5, STXBP5L,
 * TAF5, TAF5L, TBL1X, TBL1XR1, TBL1Y, TBL2, TBL3, TEP1, THOC3, THOC6, TLE1, TLE2, TLE3, TLE4, TLE6, TRAF7, TSSC1, TULP4, TUWD12,
 * UTP15, UTP18,
 * WAIT1, WDF3, WDFY1, WDFY2, WDFY3, WDFY4, WDHD1, WDR1, WDR10, WDR12, WDR13, WDR16, WDR17, WDR18, WDR19, WDR20, WDR21A, WDR21C, WDR22, WDR23, WDR24, WDR25, WDR26, WDR27, WDR3, WDR31, WDR32, WDR33, WDR34, WDR35, WDR36, WDR37, WDR38, WDR4, WDR40A, WDR40B, WDR40C, WDR41, WDR42A, WDR42B, WDR43, WDR44, WDR46, WDR47, WDR48, WDR49, WDR5, WDR51A, WDR51B, WDR52, WDR53, WDR54, WDR55, WDR57, WDR59, WDR5B, WDR6, WDR60, WDR61, WDR62, WDR63, WDR64, WDR65, WDR66, WDR67, WDR68, WDR69, WDR7, WDR70, WDR72, WDR73, WDR74, WDR75, WDR76, WDR77, WDR78, WDR79, WDR8, WDR81, WDR82, WDR85, WDR86, WDR88, WDR89, WDR90, WDR91, WDR92, WDSOF1, WDSUB1, WDTC1, WSB1, WSB2,
 * ZFP106