title: Crystal structure of archaeal homolog of proteasome-assembly chaperone PbaA.
abstract: Formation of the eukaryotic proteasome is not a spontaneous process but a highly ordered process assisted by several assembly chaperones. In contrast, archaeal proteasome subunits can spontaneously assemble into an active form. Recent bioinformatic analysis identified the proteasome-assembly chaperone-like proteins, PbaA and PbaB, in archaea. Our previous study showed that the PbaB homotetramer functions as a proteasome activator through its tentacle-like C-terminal segments. However, a functional role of the other homolog PbaA has remained elusive. Here we determined the 2.25-Å resolution structure of PbaA, illustrating its disparate tertiary and quaternary structures compared with PbaB. PbaA forms a homopentamer in which the C-terminal segments, with a putative proteasome-activating motif, are packed against the core. These findings offer deeper insights into the molecular evolution relationships between the proteasome-assembly chaperones and the proteasome activators.
authors.affiliation: School of Physical Science, The Graduate University for Advanced Studies, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan; Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan; Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
authors.forename: Arunima
authors.initials: A
authors.lastname: Sikdar
authors.affiliation: Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan; JST, PRESTO, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Satoh
authors.affiliation: Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Oho 1-1, Tsukuba, Ibaraki 305-0801, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kawasaki
authors.affiliation: School of Physical Science, The Graduate University for Advanced Studies, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan; Okazaki Institute for Integrative Bioscience and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan; Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan. Electronic address: kkatonmr@ims.ac.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Kato
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry*; D011487:Protein Conformation
chemical_list: D019843:Archaeal Proteins; D018832:Molecular Chaperones; D046988:Proteasome Endopeptidase Complex
keywords: Archaea; Proteasome activator; Proteasome-assembly chaperone; Protein degradation