WD-40 repeat family
"Receptor for activated C kinase (RACK1) is a highly conserved, eukaryotic protein of the WD-40 repeat family.  During Phaseolus vulgaris root development, RACK1 (PvRACK1) mRNA expression was induced by auxins, abscissic acid, cytokinin, and gibberellic acid."
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.

# Structure
WD40 domain-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
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 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.

# Protein family
According to the initial analysis of 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:
- 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,
- IFT121, IFT122, IFT140, IFT172, IFT80, IQWD1,
- KATNB1, KIAA1336, KIF21A, KIF21B, KM-PA-2,
- KEAP1,
- LLGL1, LLGL2, LRBA, LRRK1, LRRK2, LRWD1, LYST,
- MAPKBP1, MED16, MORG1,
- NBEA, NBEAL1, NEDD1, NLE1, NSMAF, NUP37, NUP43, NWD1,
- PAAF1, PAFAH1B1, PAK1IP1, PEX7, PHIP, PIK3R4, PLAA, PLRG1, PPP2R2A, PPP2R2B, PPP2R2C, PPP2R2D, PPWD1, PREB, PRPF19, PRPF4, PWP1, PWP2,
- RAE1, RPTOR, 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

# Hypotheses
- A1BG has no regulatory elements in either promoter for the WD-40 repeat family proteins.
- A1BG is not transcribed by a regulatory element for the WD-40 repeat family proteins.
- No regulatory element for the WD-40 repeat family proteins participates in the transcription of A1BG.

# Acknowledgements
The content on this page was first contributed by: Henry A. Hoff.