Chapter 6, Problem 15P

The CAP protein is shown bound to DNA in Fig. 6.15 on p.185. CAP binds a specific sequence of base pairs in DNA (N= any base):

5’ TGTGANNNNNNTCACA 3’

3’ ACACTNNNNNNAGTGT 5’

a.	In a long double-stranded DNA molecule with random base sequence and an equal number of A-T and G-C base pairs, how frequently would a CAP binding site be present in the DNA molecule?
b.	CAP protein binds DNA as dimer: two identical CAP protein subunits bound to each other bind DNA. Can you detect a special feature of the DNA site that CAP binds that suggests that two identical protein subunits bind the DNA? (Hint: Try reading the sequence in the 5ˈ-to-3ˈ direction on each strand.)
c.	CAP protein binds to the major groove of DNA. Do you expect that DNA helicase is required for CAP to bind DNA?