The following is a description of protein-DNA interactions by a novel
Dck is a transcription factor, activated by the Tyr kinase, Lck.
Dck is a novel TC factor, in that it has both zinc finger and leucine
zipper motifs. Upon stimulation by Lck, two Dck polypeptides
homodimerizers (Not that there is anything wrong with it) to form a
complex with two globular domains, with one protruding zinc finger. The
Zn finger is also unusual for the critical amino acid residue for DNA
interaction is His, rather than Cys. Generally, its interaction with DNA
is promiscuous, but can be a sequence specific as well. The consensus
sequence is CATXXXCAT. The homodimer initially binds DNA, causing a
slight bend in the zinc finger motif. It then slides along the DNA in
search of the CAT sequence. It will then insert at the consensus
sequence at both groove majora and minora. The CAT-DNA then unwinds,
allowing full insertion of the zinc finger motif. This interaction
results in a kink in the DNA, relieving the torque and releasing a
tremendous amount of free energy.