Cover photograph (Copyright © 2005, American Society for Microbiology. All Rights reserved.): Three different variables are mapped onto the surface of a homology model of SUMO2. The left reflection depicts the electrostatic potential, the central mirror shows the severity of alanine substitutions on SUMO-mediated transcriptional inhibition from green (mild) to red (severe), and the reflection on the right represents the evolutionary conservation from green (variable) to red (conserved). (See related article on p. 4272.)