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Publication Abstract from PubMed

The 26S proteasome proteolyses ubiquitylated proteins and is assembled from a 20S proteolytic core and two 19S regulatory particles (19S-RP). The 19S-RP scaffolding subunits Rpn1 and Rpn2 function to engage ubiquitin receptors. Rpn1 and Rpn2 are characterized by eleven tandem copies of a 35-40 amino acid repeat motif termed the proteasome/cyclosome (PC) repeat. Here, we reveal that the eleven PC repeats of Rpn2 form a closed toroidal structure incorporating two concentric rings of alpha helices encircling two axial alpha helices. A rod-like N-terminal domain consisting of 17 stacked alpha helices and a globular C-terminal domain emerge from one face of the toroid. Rpn13, an ubiquitin receptor, binds to the C-terminal 20 residues of Rpn2. Rpn1 adopts a similar conformation to Rpn2 but differs in the orientation of its rod-like N-terminal domain. These findings have implications for understanding how 19S-RPs recognize, unfold, and deliver ubiquitylated substrates to the 20S core.

The Structure of the 26S Proteasome Subunit Rpn2 Reveals Its PC Repeat Domain as a Closed Toroid of Two Concentric alpha-Helical Rings.,He J, Kulkarni K, da Fonseca PC, Krutauz D, Glickman MH, Barford D, Morris EP Structure. 2012 Mar 7;20(3):513-21. PMID:22405010^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.