Laser spotlight reveals machine 'climbing' DNA
New imaging technology has revealed how the molecular machines that remodel genetic material inside cells 'grab onto' DNA like a rock climber looking for a handhold. The experiments, reported in this week's Science , use laser light to generate very bright patches close to single cells. When coupled with fluorescent tags this 'spotlight' makes it possible to image the inner workings of cells fast enough to see how the molecular machines inside change size, shape, and composition in the presence of DNA. The Oxford team built their own light microscopy technology for the study, which is a collaboration between the research groups of Mark Leake in Oxford University's Department of Physics and David Sherratt in Oxford University's Department of Biochemistry. The molecular machines in question are called Structural Maintenance of Chromosome (SMC) complexes: they remodel the genetic material inside every living cell and work along similar principles to a large family of molecules that act as very small motors performing functions as diverse as trafficking vital material inside cells to allowing muscles to contract. The researchers studied a particular SMC, MukBEF (which is made from several different protein molecules), inside the bacterium E.coli . David Sheratt and his team found a way to fuse 'fluorescent proteins' directly to the DNA coding for MukBEF, effectively creating a single dye tag for each component of these machines.
