title: Localization of the regulatory particle subunit Sem1 in the 26S proteasome.
abstract: The ubiquitin-proteasome system is responsible for regulated protein degradation in the cell with the 26S proteasome acting as its executive arm. The molecular architecture of this 2.5 MDa complex has been established recently, with the notable exception of the small acidic subunit Sem1. Here, we localize the C-terminal helix of Sem1 binding to the PCI domain of the subunit Rpn7 using cryo-electron microscopy single particle reconstruction of proteasomes purified from yeast cells with sem1 deletion. The approximate position of the N-terminal region of Sem1 bridging the cleft between Rpn7 and Rpn3 was inferred based on site-specific cross-linking data of the 26S proteasome. Our structural studies indicate that Sem1 can assume different conformations in different contexts, which supports the idea that Sem1 functions as a molecular glue stabilizing the Rpn3/Rpn7 heterodimer.
authors: Max-Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany.
authors: Stefan
authors: S
authors: Bohn
authors: Eri
authors: E
authors: Sakata
authors: Florian
authors: F
authors: Beck
authors: Ganesh R
authors: GR
authors: Pathare
authors: Jérôme
authors: J
authors: Schnitger
authors: Istvan
authors: I
authors: Nágy
authors: Wolfgang
authors: W
authors: Baumeister
authors: Friedrich
authors: F
authors: Förster
mesh_terms: D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry*; D021122:Protein Subunits / Q000737:chemistry; D050436:Regulatory Elements, Transcriptional; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*
chemical_list: D021122:Protein Subunits; C117424:SEM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease