Promiscuity in Protein DNA Interactions

Beavis N Butthead BNB at lost.cause
Thu Jun 1 19:22:04 EST 1995


The following is a description of protein-DNA interactions by a novel 
proto-oncogene, Dck:
	
	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.







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