According to the starch–statolith hypothesis, columella of the root cap cells represent statocytes, or gravity-sensing cells

TLS Online TPP Program

#Id: 6482

#Unit 3. Fundamental Processes

Sp1 contains three zinc fingers, 25% of their amino acid residues are Gln

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.