BIOL308 Lecture 8: Lecture 8
8 Apr 2016
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Document Summary
Negative supercoils store energy energy of negative supercoils can be converted into untwisting (unwinding) of double helix. Dna overwound - positive supercoiling: reduced chance for dna-protein interaction. Dna underwound - negative supercoils negative supercoils store energy that could help strand separation - untwisting favored (important for replication and transcription) Topoisomerases are enzymes that recognize and regulate supercoiling and play an important role in replication and transcription. Reverse gyrase - first discovered in the hyperthermophilic archaebacterium, sulfolobus. Topoisomerase ii, not topoisomerase i, is the proficient relaxase of nucleosomal dna. The embo journal (2006), 25, - 2575 - 2583, Makes double-stranded cut, pass a duplex dna through it and re-seals the cut. Circular dna example, but the same for linear if ends are not free to rotate. Breaks dna strand (tyr residue attacks backbone phosphate) - formation of phosphotyrosine bond. Passes the other strand through the break and reseal dna.
