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| PROSITE documentation PDOC00574 |
β-transducin (G-β) is one of the three subunits (α, β, and γ) of the guanine nucleotide-binding proteins (G proteins) which act as intermediaries in the transduction of signals generated by transmembrane receptors [1]. The α subunit binds to and hydrolyzes GTP; the functions of the β and γ subunits are less clear but they seem to be required for the replacement of GDP by GTP as well as for membrane anchoring and receptor recognition.
In higher eukaryotes G-β exists as a small multigene family of highly conserved proteins of about 340 amino acid residues. Structurally G-β consists of eight tandem repeats of about 40 residues, each containing a central Trp-Asp motif (this type of repeat is sometimes called a WD-40 repeat). Such a repetitive segment has been shown [2,3,4,5] to exist in a number of other proteins listed below:
- Yeast STE4, a component of the pheromone response pathway. STE4 is a G-β like protein that associates with GPA1 (G-α) and STE18 (G-γ).
- Yeast MSI1, a negative regulator of RAS-mediated cAMP synthesis. MSI1 is most probably also a G-β protein.
- Human and chicken protein 12.3. The function of this protein is not known, but on the basis of its similarity to G-β proteins, it may also function in signal transduction.
- Chlamydomonas reinhardtii gblp. This protein is most probably the homolog of vertebrate protein 12.3.
- Human LIS1, a neuronal protein involved in type-1 lissencephaly.
- Mammalian coatomer β' subunit (β'-COP), a component of a cytosolic protein complex that reversibly associates with Golgi membranes to form vesicles that mediate biosynthetic protein transport.
- Yeast CDC4, essential for initiation of DNA replication and separation of the spindle pole bodies to form the poles of the mitotic spindle.
- Yeast CDC20, a protein required for two microtubule-dependent processes: nuclear movements prior to anaphase and chromosome separation.
- Yeast MAK11, essential for cell growth and for the replication of M1 double-stranded RNA.
- Yeast PRP4, a component of the U4/U6 small nuclear ribonucleoprotein with a probable role in mRNA splicing.
- Yeast PWP1, a protein of unknown function.
- Yeast SKI8, a protein essential for controlling the propagation of double- stranded RNA.
- Yeast SOF1, a protein required for ribosomal RNA processing which associates with U3 small nucleolar RNA.
- Yeast TUP1 (also known as AER2 or SFL2 or CYC9), a protein which has been implicated in dTMP uptake, catabolite repression, mating sterility, and many other phenotypes.
- Yeast YCR57c, an ORF of unknown function from chromosome III.
- Yeast YCR72c, an ORF of unknown function from chromosome III.
- Slime mold coronin, an actin-binding protein.
- Slime mold AAC3, a developmentally regulated protein of unknown function.
- Drosophila protein Groucho (formerly known as E(spl); 'enhancer of split'), a protein involved in neurogenesis and that seems to interact with the Notch and Delta proteins.
- Drosophila TAF-II-80, a protein that is tightly associated with TFIID.
The number of repeats in the above proteins varies between 5 (PRP4, TUP1, and Groucho) and 8 (G-β, STE4, MSI1, AAC3, CDC4, PWP1, etc.). In G-β and G-β like proteins, the repeats span the entire length of the sequence, while in other proteins, they make up the N-terminal, the central or the C-terminal section.
A signature pattern can be developed from the central core of the domain (positions 9 to 23).
Two profiles were developed for this module, the first one picks up WD repeats while the second profile is 'circular' and will thus detect a region containing adjacent WD repeats.
Last update:December 2004 / Pattern and text revised.
PROSITE methods (with tools and information) covered by this documentation:
| 1 | Authors | Gilman A.G. |
| Title | G proteins: transducers of receptor-generated signals. | |
| Source | Annu. Rev. Biochem. 56:615-649(1987). | |
| PubMed ID | 3113327 | |
| DOI | 10.1146/annurev.bi.56.070187.003151 |
| 2 | Authors | Duronio R.J., Gordon J.I., Boguski M.S. |
| Title | Comparative analysis of the beta transducin family with identification of several new members including PWP1, a nonessential gene of Saccharomyces cerevisiae that is divergently transcribed from NMT1. | |
| Source | Proteins 13:41-56(1992). | |
| PubMed ID | 1594577 |
| 3 | Authors | van der Voorn L., Ploegh H.L. |
| Source | FEBS Lett. 307:131-134(1992). |
| 4 | Authors | Neer E.J., Schmidt C.J., Nambudripad R., Smith T.F. |
| Title | The ancient regulatory-protein family of WD-repeat proteins. | |
| Source | Nature 371:297-300(1994). | |
| PubMed ID | 8090199 | |
| DOI | 10.1038/371297b0 |
| 5 | Authors | Smith T.F., Gaitatzes C., Saxena K., Neer E.J. |
| Title | The WD repeat: a common architecture for diverse functions. | |
| Source | Trends Biochem. Sci. 24:181-185(1999). | |
| PubMed ID | 10322433 |
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