Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): A metaphorical representation of the “substrate channeling” phenomenon using an inner-city canal from the Scottish capital, Edinburgh. NDPK-A and AMPK α1 act as controllers for the flow of cellular energy, important in various disease states, as indicated. The proteins act as “canal locks,” where NDPK-A channels ATP to AMPKα1, independent of the surrounding cellular energy status. CF, cystic fibrosis. The photograph was designed by K. Clarke and R. Crawford. (See related article on page 5921.)