Sharper image of fatty acid synthase

The gargantuan 2.6-megadalton protein complex that catalyzes the iterative assembly of fungal fatty acids has just come into sharper focus. Nenad Ban and colleagues at the Swiss Federal Institute of Technology, Zurich, slimmed down their previous 5.0-?? resolution X-ray structure of the synthase to 3.1-?? resolution and suggest how this monster enzyme catalyzes a total of 42 reaction steps to create an 18-carbon chain (Science 2007, 316, 254). The protein has two reaction chambers with three full sets of active sites, so six fatty acids can be synthesized simultaneously. A special carrier protein shuttles intermediates around the reaction chamber; the fatty acid chain length increases by two carbons with each cycle. A second paper by Ban's group reveals that the carrier protein places a fatty acid intermediate in a ketoacyl synthase active site as if the intermediate were at the end of an opening switchblade (Science 2007, 316, 288).