title: The 19S cap puzzle: a new jigsaw piece.
abstract: After elucidation of the atomic details of 20S proteasomes, current research focuses on the regulatory 19S particle. In this issue of Structure, He et al. present the crystal structure of Rpn2 and use electron microscopy to examine differences between Rpn2 and Rpn1.
authors.affiliation: Center for Integrated Protein Science, Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Garching D-85747, Germany.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Huber
authors.forename: Michael
authors.initials: M
authors.lastname: Groll