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what does Helicase require to separate DNA strands?
ATP
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what gene encodes for helicase gene?
dnaB in E. coli
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what are the other functions of helicases, besides DNA replication?
DNA recombination, termination of transcription DNA splicing and RNA editing
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what is the structure of helicase?
monomer with 4 domains, A1 has p loop
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how does a helicase work?
- A1 and B1 bind ssDNA (nothign in ATP site)
- ATP binds and induces a conformational change (A1 releases DNA as it moves close to B1)
- reverse conformational change after ATP hydrolysis, B1 and A1 separate (DNA is pulled along with this motion)
- ATP hydrolyzed to ADP wit has weak interaction with protein, then it is released
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describe the binding of single stranded binding protein.
- tight binding to ssDNA, weak bindin to dsDNA
- no sequence specificity, binding is electrostatic to the negative charges on the phosphate backbone
- cooperative binding
- rate of replication is 10 fold higher with SBB present
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what are the functions of the subunits in DNA Pol III?
- alpha (ability to synthesize DNA
- e (3 to 5 proofreading
- theta: required for assembly
- Beta 2 sliding clamp
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