The NO synthases structures have been elusive so far. As these are fairly complex structures with different functional domains this is not very surprising. The role of these molecules in signal transduction is established and errors therein might lead to hypertension, erectile dysfunction, neurodegeneration, stroke or heart disease.

A PNAS paper this week has solved all the three structures of eNOS, iNOS, and nNOS. They used a high through put Electron microscopy single particle method to obtain the many different conformation in which these enzyme occurs. They have also solved the role of calmodulin in the enzymatic reaction and shown why the binding of calmodulin is a time limiting step (for two of the enzymes). Given the complexity of the molecular structures shown and the different confirmation obtained this is some nice piece of work: from the structure to the function. Beautifully done!