TATA Binding Protein

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TATA box binding protein
Cartoon of the TATA binding protein structure
Symbol(s):	TBP GTF2D1, SCA17
Genetic data
Locus:	Chr. 6 q27
Protein Structure/Function
Protein length:	339 (Amino Acids)
Molecular Weight:	37698 (Da)
Motifs:	CC motif
Other
Taxa expressing:	Homo sapiens; homologs many metazoan taxa
Cell types:	ubiquitous
Subcellular localization:	nucleus
Pathway(s):	Basal transcription factors (KEGG)

TBP (TATA Binding Protein) is a DNA binding protein that binds sequence specifically to the TATA box found in gene promoters.

TBP is vital for all eukaryote transcription, and will in some cases be forced to bind non sequence specifically. It is involved in DNA melting (double strand separation) and on binding bends the DNA through 90° (the AT-rich sequence to which it binds facilitates easy melting). The TBP is an unusual protein in that it binds the minor groove and binds with a β sheet.

[edit] Role as Transcription Factor Subunit

TBP is a subunit of the eukaryotic transcription factor TFIID. TFIID is the first protein to bind to DNA during the formation of the pre-initiation transcription complex of RNA polymerase II (RNA Pol II). Binding of TFIID to the TATA box in the promoter region of the gene initiates the recruitment of other factors required for RNA Pol II to begin transcription. Some of the other recruited transcription factors include TFIIA, TFIIB, TFIID, and TFIIF. Each of these transcription factors are formed from the interaction of many protein subunits, indicating that transcription is a heavily regulated process.

TBP is also a necessary component of RNA polymerase I and RNA polymerase III, and is perhaps the only common subunit required by all three of the RNA polymerases.

[edit] DNA-Protein Interactions

When TBP binds to a TATA box within the DNA, it distorts the DNA by creating a nearly 90 degree bend. The distortion is accomplished through a great amount of surface contact between the protein and DNA. TBP binds with the negatively charged phosphates in the DNA backbone through positively charged lysine and arginine amino acid residues. The sharp bend in the DNA is produced through projection of four bulky phenylalanine residues into the minor groove. As the DNA bends, its contact with TBP increases, thus enhancing the DNA-protein interaction.

The strain imposed on the DNA through this interaction initiates melting, or separation, of the strands. Because this region of DNA is rich in adenine and thymine residues, which base pair through only two hydrogen bonds, the DNA strands are more easily separated. Separation of the two strands exposes the bases and allows RNA polymerase II to begin transcription of the gene.

For information on the use of TBP in cells see: RNA polymerase I, RNA polymerase II and RNA polymerase III.