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what does Helicase require to separate DNA strands?
what gene encodes for helicase gene?
dnaB in E. coli
what are the other functions of helicases, besides DNA replication?
DNA recombination, termination of transcription DNA splicing and RNA editing
what is the structure of helicase?
monomer with 4 domains, A1 has p loop
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
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
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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