- 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. . pmid:17334374.
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.