- Spring 2007
- Location: BRB 603. Wednesdays from 9:30 - 11:30 (practice and review session) and Thursdays (The Real Thang) from 10:30 - 12:30
- How the Class Works
Week-by-Week Schedule Summary
- Enlist a faculty mentor
- send them the paper
- make sure the date works
- vote by wiki?
- Make sure there is consensus (excitement) among remaining class members about the proposed paper
- again, vote can be done on wiki
Proposed Paper for Discussion--Contact Chayne for inquiries
- Nöllmann M, Stone MD, Bryant Z, Gore J, Crisona NJ, Hong SC, Mitelheiser S, Maxwell A, Bustamante C, and Cozzarelli NR. Multiple modes of Escherichia coli DNA gyrase activity revealed by force and torque. Nat Struct Mol Biol. 2007 Apr;14(4):264-71. DOI:10.1038/nsmb1213 |
E. coli DNA gyrase uses the energy of ATP hydrolysis to introduce essential negative supercoils into the genome, thereby working against the mechanical stresses that accumulate in supercoiled DNA. Using a magnetic-tweezers assay, we demonstrate that small changes in force and torque can switch gyrase among three distinct modes of activity. Under low mechanical stress, gyrase introduces negative supercoils by a mechanism that depends on DNA wrapping. Elevated tension or positive torque suppresses DNA wrapping, revealing a second mode of activity that resembles the activity of topoisomerase IV. This 'distal T-segment capture' mode results in active relaxation of left-handed braids and positive supercoils. A third mode is responsible for the ATP-independent relaxation of negative supercoils. We present a branched kinetic model that quantitatively accounts for all of our single-molecule results and agrees with existing biochemical data.
- make sure each of you has a slot as presenter 1 and 2.