Ecosystem - A structural and functional unit of ecology where the living organisms interact with each other and the surrounding environment

TLS Online TPP Program

#Id: 6483

#Unit 3. Fundamental Processes

For RNA polymerase II, the positioning factor is TFIID, which consists of TBP associated with up to 14 other subunits called TAFs (for TBP -associated factors). 

TLS Online TPP Program

#Id: 6484

#Unit 3. Fundamental Processes

The total mass of TFIID typically is -800 kD

TAF has 2 enzymatic activities:

Histone acetyltransferase

Protein kinase

TLS Online TPP Program

#Id: 6485

#Unit 3. Fundamental Processes

Model for the Interaction Between TBP and Promoters

TLS Online TPP Program

#Id: 6486

#Unit 3. Fundamental Processes

TBP Binds to and Distorts DNA Using a b Sheet Inserted into the Minor Groove

TBP uses an extensive region of  sheet to recognize the minor groove of the TATA element . This is unusual. More typically, proteins recognize DNA using  helices inserted into the major groove of DNA, as we have seen and also for the factor .

TLS Online TPP Program

#Id: 6487

#Unit 3. Fundamental Processes

TBP–DNA complex. TBP (purple) is complexed with the DNA TATA sequence (gray) found at the start of many Pol II genes. 

TLS Online TPP Program

#Id: 6488

#Unit 3. Fundamental Processes

TBP causes the minor groove to be widened to an almost flat conformation; it also bends the DNA by an angle of 80. The interaction between TBP and DNA involves only a limited number of hydrogen bonds between the protein and the edges of the base pairs in the minor groove.  Instead, much of the specificity is imposed by two pairs of phenylalanine side chains that intercalate between the base pairs at either end of the recognition sequence and drive the strong bend in the DNA.