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Updated: Jul 17, 2026

Examining Proteasome Assembly with Recombinant Archaeal Proteasomes and Nondenaturing PAGE: The Case for a Combined Approach
Published on: December 17, 2016
Molecular basis for the subunit assembly of the primase from an archaeon Pyrococcus horikoshii
Nobutoshi Ito1, Ikuo Matsui, Eriko Matsui
1Cellular Physiology Laboratory, Discovery Research Institute, RIKEN, Wako, Saitama, Japan.
Abstract:
Archaeal/eukaryotic primases form a heterodimer consisting of a small catalytic subunit (PriS) and a large subunit (PriL). The heterodimer complex synthesizes primer oligoribonucleotides that are required for chromosomal replication. Here, we describe crystallographic and biochemical studies of the N-terminal domain (NTD) of PriL (PriL(NTD); residues 1-222) that bind to PriS from a hyperthermophilic archaeon, Pyrococcus horikoshii, at 2.9 A resolution. The PriL(NTD) structure consists of two subdomains, the helix-bundle and twisted-strand domains. The latter is structurally flexible, and is expected to contain a PriS interaction site. Pull-down and surface plasmon resonance analyses of structure-based deletion and alanine scanning mutants showed that the conserved hydrophobic Tyr155-Tyr156-Ile157 region near the flexible region is the PriS-binding site, as the Y155A/Y156A/I157A mutation markedly reduces PriS binding, by 1000-fold. These findings and a structural comparison with a previously reported PriL(NTD)-PriS complex suggest that the presented alternative conformations of the twisted-strand domain facilitate the heterodimer assembly.
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