Transformative encounters

摘要

Ubiquitin and ubiquitin-like (Ubl) proteins function by becoming attached to their target proteins and modulating the activities of those targets in various ways. They thus regulate many physiological and disease-related processes including embryonic development, the immune response, viral infection and cancer-cell division. Three types of evolutionarily conserved enzymes - E1 activating enzymes, E2 conjugating enzymes and E3 ligase enzymes - act sequentially through parallel yet distinct pathways to conjugate ubiquitin and Ubl proteins, such as SUMO and NEDD8, to their targets. In a landmark paper on page 906 of this issue, Lima, Tan and their colleagues (Olsen et al.) share structural data that provide intimate glimpses into exactly how an El enzyme activates SUMO, a process in which El and SUMO become transiently linked. Their observations solve long-standing mysteries about Ubl-protein activation.