The TATA binding protein is critical for transcription by all three eukaryotic RNA polymerases. It acts as the heart of the central subunits of SL1, TFIID, and TFIIIB in class I, II, and III promotors respectively. In addition, TBP is found in many organisms including yeast, fruit flies, plants, and humans. In fact, the TBP domains are almost 80% conserved among these species.
The saddle shaped protein contains 180 amino acids and recognizes (in most circumstances) a 6 base pair consensus TATAAA (better known as the TATA box). The TBP is unique in the respect that it binds the DNA at the minor groove, bending the DNA at an 80 degree angle.